Light emitting semiconductor device

ABSTRACT

An embodiment includes a semiconductor device including a semiconductor structure including a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; a first insulation layer disposed on the semiconductor structure; a first electrode disposed on the first conductive semiconductor layer; a second electrode disposed on the second conductive semiconductor layer; a first cover electrode disposed on the first electrode; a second cover electrode disposed on the second electrode; and a second insulation layer extending from an upper surface of the first cover electrode to an upper surface of the second cover electrode. The semiconductor structure includes a first surface extending from an upper surface of the first conductive semiconductor layer where the first electrode is disposed to a side surface of the active layer and an upper surface of the second conductive semiconductor where the second electrode is disposed. The first insulation layer is disposed on the first surface to be spaced apart from the first electrode. The first insulation layer is disposed on the first surface to overlap with the first cover electrode in a first direction perpendicular to the upper surface of the first conductive semiconductor layer.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a U.S. National Stage Application under 35 U.S.C. §371 of PCT Application No. PCT/KR2017/009954, filed Sep. 11, 2017, whichclaims priority to Korean Patent Application No. 10-2016-0116886, filedSep. 10, 2016; Korean Patent Application No. 10-2016-0118241, filed Sep.13, 2016; Korean Patent Application No. 10-2016-0118242, filed Sep. 13,2016; and Korean Patent Application No. 10-2017-0096477, filed Jul. 28,2017, whose entire disclosures are hereby incorporated by reference.This application is related to U.S. application Ser. No. 15/692,617,filed Aug. 31, 2017; U.S. application Ser. No. 15/821,519, filed Nov.22, 2017; U.S. application Ser. No. 16/100,785, filed Aug. 10, 2018;U.S. application Ser. No. 16/310,340, filed Dec. 14, 2018; and U.S.application Ser. No. 16/331,039 filed Mar. 6, 2019, whose disclosuresare also incorporated by reference.

TECHNICAL FIELD

Embodiments relate to semiconductor devices.

BACKGROUND ART

Semiconductor devices including compounds such as GaN and AlGaN havemany merits such as wide and adjustable band gap energy and thus may bevariously used as light emitting devices, light receiving devices,various kinds of diodes, or the like.

In particular, light emitting devices using group III-V or II-VIcompound semiconductors or light emitting devices such as a laser diodemay implement various colors such as red, green, blue, and ultravioletdue to the development of thin film growth technology and devicematerials, and may implement efficient white light rays by usingfluorescent materials or combining colors. These light emitting devicesalso have advantages with respect to low power consumption,semi-permanent life span, fast response time, safety, and environmentalfriendliness compared to conventional light sources such as afluorescent lamp, an incandescent lamp, or the like.

In addition, when light receiving devices such as optical detectors orsolar cells are produced using group III-V or II-VI compoundsemiconductors, an optical current may be generated by light absorptionin various wavelength ranges through development of device materials.Thus, light may be used in various wavelength ranges from gamma rays toradio wavelength regions. Also, the light receiving devices have theadvantages of fast response time, stability, environmental friendliness,and ease of adjustment of device materials and may be easily used topower control or microwave circuits or communication modules.

Accordingly, semiconductor devices are being extensively used in thetransmission modules of optical communication means, light emittingdiode backlights substituted for cold cathode fluorescence lamps (CCFL)forming the backlights of liquid crystal display (LCD) devices, whitelight emitting diode lamps to be substituted for fluorescent bulbs orincandescent bulbs, car headlights, traffic lights, and sensors fordetecting gas or fire. In addition, semiconductor devices may also beextensively used in high-frequency application circuits or other powercontrol devices and even communication modules.

In particular, a light emitting device that emits light in anultraviolet wavelength range may be used for curing, medical, andsterilization purposes due to its curing or sterilizing action.

Recently, research on ultraviolet light emitting devices has beenactively conducted, but the ultraviolet light emitting devices aredifficult to implement as a vertical or flip chip and also haverelatively low light extraction efficiency.

SUMMARY

An embodiment provides a semiconductor device having enhanced lightextraction efficiency.

An embodiment provides a semiconductor device having good electriccurrent spreading efficiency.

An embodiment provides a flip-chip-type ultraviolet light emittingdevice.

An embodiment provides a semiconductor device having an improvedoperating voltage.

An embodiment provides a semiconductor device having enhanced opticaloutput power.

Problems to be solved in the embodiments are not limited thereto, andinclude the following technical solutions and objectives of effectsunderstandable from the embodiments.

According to an embodiment of the present invention, a semiconductordevice includes a semiconductor structure including a first conductivesemiconductor layer, a second conductive semiconductor layer, and anactive layer disposed between the first conductive semiconductor layerand the second conductive semiconductor layer; a first insulation layerdisposed on the semiconductor structure; a first electrode disposed onthe first conductive semiconductor layer; a second electrode disposed onthe second conductive semiconductor layer; a first cover electrodedisposed on the first electrode; a second cover electrode disposed onthe second electrode; and a second insulation layer extending from anupper surface of the first cover electrode to an upper surface of thesecond cover electrode. The semiconductor structure includes a firstsurface extending from an upper surface of the first conductivesemiconductor layer where the first electrode is disposed to a sidesurface of the active layer and an upper surface of the secondconductive semiconductor where the second electrode is disposed. Thefirst insulation layer is disposed on the first surface to be spacedapart from the first electrode. The first insulation layer is disposedon the first surface to overlap with the first cover electrode in afirst direction perpendicular to the upper surface of the firstconductive semiconductor layer.

The first insulation layer and the first electrode may have a separationdistance greater than 0 μm and less than 4 μm.

The first insulation layer may be disposed on the first surface to bespaced apart from the second electrode, and the first insulation layermay be disposed on the first surface to overlap with the first secondelectrode in the first direction.

The first electrode may include a first groove disposed on an uppersurface thereof and a protrusion portion surrounding the first groove,and the first cover electrode may be disposed on the first groove andthe protrusion portion.

Advantageous Effects

According to an embodiment, it is possible to enhance light extractionefficiency.

It is also possible to enhance optical output power due to good electriccurrent spreading efficiency.

It is also possible to lower an operating voltage.

Various advantageous merits and effects of the present invention are notlimited to the above-descriptions and will be easily understood whileembodiments of the present invention are described in detail.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view of a semiconductor device according to afirst embodiment of the present invention.

FIGS. 2 and 3 are views illustrating a configuration in which opticaloutput power is enhanced depending on a change in number of recesses.

FIG. 4 is an enlarged view of a part A of FIG. 1 .

FIG. 5 is an enlarged view of a part B of FIG. 3 .

FIG. 6 is an enlarged view of a part C of FIG. 4 .

FIG. 7 is a diagram showing a layer structure of a first electrode and areflective layer.

FIG. 8A is a first modification of FIG. 6 .

FIG. 8B is a second modification of FIG. 6 .

FIG. 9 is a third modification of FIG. 6 .

FIG. 10 is a diagram showing various shapes of a reflective layer.

FIG. 11 is a conceptual view of a semiconductor device according to asecond embodiment of the present invention.

FIG. 12 is a sectional view of a semiconductor device according to athird embodiment of the present invention.

FIG. 13A is an enlarged view of a part A of FIG. 12 .

FIG. 13B is a modification of FIG. 13A.

FIG. 14A is a plan view of the semiconductor device according to thethird embodiment of the present invention.

FIG. 14B is a plan view showing an etching region of a first electrodeaccording to the third embodiment of the present invention.

FIG. 14C is a modification of FIG. 14B.

FIG. 14D is a plan view showing a first cover electrode and a secondcover electrode according to the third embodiment of the presentinvention.

FIG. 14E is a modification of FIG. 14D.

FIGS. 15A and 15B are a plan view and a sectional view in which a lightemitting region is formed through mesa etching.

FIGS. 16A and 16B are a plan view and a sectional view in which a firstelectrode is formed.

FIGS. 17A and 17B are a plan view and a sectional view in which a secondelectrode is formed.

FIGS. 18A and 18B are a plan view and a sectional view in which a firstgroove is formed by etching a first electrode.

FIGS. 19A and 19B are a plan view and a sectional view in which a firstcover electrode and a second cover electrode are formed.

FIGS. 20A and 20B are a plan view and a sectional view in which a secondinsulation layer is formed.

FIG. 21 is a photograph obtained by capturing a plane surface of asemiconductor device according to the third embodiment of the presentinvention.

FIG. 22 is a photograph obtained by capturing a sectional surface of asemiconductor device according to the third embodiment of the presentinvention.

FIG. 23 is a diagram showing a semiconductor device package according tothe third embodiment of the present invention.

FIG. 24 is a conceptual view of a semiconductor structure according toan embodiment of the present invention.

FIG. 25 is a graph obtained by measuring an aluminum composition of asemiconductor structure.

FIG. 26 is a conceptual view of a semiconductor device according to afourth embodiment of the present invention.

FIG. 27 is a plan view of FIG. 26 .

FIG. 28 is a sectional view taken along A-A of FIG. 27 .

FIG. 29 is a plan view of a second conductive layer.

FIG. 30 is a plan view showing a second conductive layer having aminimum area.

FIG. 31 is a plan view showing a second conductive layer having aminimum area.

FIG. 32 is a diagram illustrating a configuration of the secondconductive layer.

FIG. 33 is a first modification of FIG. 32 .

FIG. 34 is a second modification of FIG. 32 .

FIG. 35 is a conceptual view of a semiconductor device according to afifth embodiment of the present invention.

FIG. 36 is a plan view of FIG. 35 .

FIG. 37 is an enlarged view of a part B-1 of FIG. 36 .

FIG. 38 is an enlarged view of a part B-2 of FIG. 36 .

FIG. 39 is a sectional view taken along B-B of FIG. 37 .

FIG. 40 is a first modification of FIG. 39 .

FIG. 41A is a second modification of FIG. 39 .

FIG. 41B is a plan view of the second modification.

FIG. 42 is a third modification of FIG. 39 .

FIG. 43 is a conceptual view of a semiconductor device according to asixth embodiment of the present invention.

FIG. 44 is a plan view of FIG. 43 .

FIG. 45 is a sectional view taken along C-C of FIG. 44 .

FIG. 46 is a first modification of FIG. 45 .

FIG. 47 is a second modification of FIG. 45 .

FIG. 48 is a conceptual view of a semiconductor device package accordingto an embodiment of the present invention.

FIG. 49 is a plan view of a semiconductor device package according to anembodiment of the present invention.

FIG. 50 is a modification of FIG. 49 .

DETAILED DESCRIPTION

The following embodiments may be modified or combined with each other,and the scope of the present invention is not limited to theembodiments.

Details described in a specific embodiment may be understood asdescriptions associated with other embodiments unless otherwise statedor contradicted even if there is no description thereof in the otherembodiments.

For example, when features of element A are described in a specificembodiment and features of element B are described in anotherembodiment, an embodiment in which element A and element B are combinedwith each other should be understood as falling within the scope of thepresent invention unless otherwise stated or contradicted even if notexplicitly stated.

In the descriptions of embodiments, when an element is referred to asbeing above or under another element, the two elements may be in directcontact with each other, or one or more other elements may be disposedbetween the two elements. In addition, the term “above or under” usedherein may represent a downward direction in addition to an upwarddirection with respect to one element.

Hereinafter, example embodiments will be described in detail withreference to the accompanying drawings so that they can be easilypracticed by those skilled in the art.

FIG. 1 is a conceptual view of a semiconductor device according to afirst embodiment of the present invention.

Referring to FIG. 1 , the semiconductor device according to anembodiment includes a semiconductor structure 120 including a firstconductive semiconductor layer 124, a second conductive semiconductorlayer 127, and an active layer 126 disposed between the first conductivesemiconductor layer 124 and the second conductive semiconductor layer127.

The semiconductor structure 120 according to an embodiment of thepresent invention may output ultraviolet wavelength light. For example,the semiconductor structure 120 may output near-ultraviolet wavelengthlight (UV-A), far-ultraviolet wavelength light (UV-B), ordeep-ultraviolet wavelength light (UV-C). The wavelength range may bedetermined by the aluminum composition of the semiconductor structure120.

For example, the near-ultraviolet wavelength light (UV-A) may have awavelength ranging from 320 nm to 420 nm, the far-ultraviolet wavelengthlight (UV-B) may have a wavelength ranging from 280 nm to 320 nm, andthe deep-ultraviolet wavelength light (UV-C) may have a wavelengthranging from 100 nm to 280 nm.

The first conductive semiconductor layer 124 may be made of a groupIII-V or group II-VI compound semiconductor and may be doped with afirst dopant. The first conductive semiconductor layer 124 may be madeof a material selected from among semiconductor materials having anempirical formula Inx1Aly1Ga1-x1-y1N (0≤x≤1≤1, 0≤y≤1≤1, and 0≤x1+y1≤1),for example, GaN, AlGaN, InGaN, InAlGaN, and so on. Also, the firstdopant may be an n-type dopant such as Si, Ge, Sn, Se, and Te. When thefirst dopant is an n-type dopant, the first conductive semiconductorlayer 124 doped with the first dopant may be an n-type semiconductorlayer.

The active layer 126 is disposed between the first conductivesemiconductor layer 124 and the second conductive semiconductor layer127. The active layer 126 is a layer in which electrons (or holes)injected through the first conductive semiconductor layer 124 arecombined with holes (or electrons) injected through the secondconductive semiconductor layer 127. The active layer 126 may transitionto a lower energy level due to recombination between an electron and ahole and generate light having an ultraviolet wavelength.

The active layer 126 may have, but is not limited to, any one of asingle-well structure, a multi-well structure, a single-quantum-wellstructure, a multi-quantum-well (MQW) structure, a quantum dotstructure, and a quantum wire structure.

The second conductive semiconductor layer 127 may be formed on theactive layer 126 and may be made of a group III-V or group II-VIcompound semiconductor. Also, the second conductive semiconductor layer127 may be doped with a second dopant. The second conductivesemiconductor layer 127 may be made of a semiconductor material havingan empirical formula Inx5Aly2Ga1-x5-y2N (0≤x5≤1, 0≤y2≤1, and 0≤x5+y2≤1)or a material selected from among AlInN, AlGaAs, GaP, GaAs, GaAsP, andAlGaInP. When the second dopant is a p-type dopant such as Mg, Zn, Ca,Sr, and Ba, the second conductive semiconductor layer 127 doped with thesecond dopant may be a p-type semiconductor layer.

A plurality of recesses 128 may be disposed from a first surface 127G ofthe second conductive semiconductor layer 127 even to a portion of thefirst conductive semiconductor layer 124 through the active layer 126. Afirst insulation layer 131 may be disposed inside each of the recesses128 to electrically insulate a first conductive layer 165 from thesecond conductive semiconductor layer 127 and the active layer 126.

A first electrode 142 may be disposed on top of each of the recesses 128and electrically connected with the first conductive semiconductor layer124. A second electrode 246 may be disposed on the first surface 127G ofthe second conductive semiconductor layer 127.

The first surface 127G of the second conductive semiconductor layer 127where the second electrode 246 is disposed may be made of AlGaN.However, the present invention is not limited thereto, a GaN layerhaving a small band gap may be disposed between the first surface 127Gand the second electrode 246 in order to increase electric currentinjection efficiency.

Each of the first electrode 142 and the second electrode 246 may be anohmic electrode. Each of the first electrode 142 and the secondelectrode 246 may be made of at least one of indium tin oxide (ITO),indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminumzinc oxide (IAZO), indium gallium zinc oxide (IGZO), indium gallium tinoxide (IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO),gallium zinc oxide (GZO), IZO nitride (IZON), Al—Ga ZnO (AGZO), In—GaZnO (IGZO), ZnO, IrOx, RuOx, NiO, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO,Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, Mg, Zn, Pt, Au, and Hf, butis not limited thereto.

A second electrode pad 166 may be disposed in an edge of thesemiconductor device. The second electrode pad 166 may have a recessedcentral portion and thus have a top surface including a concave portionand a convex portion. A wire (not shown) may be bonded to the concaveportion of the top surface. Accordingly, since the bonding areaincreases, the second electrode pad 166 may be strongly bonded to thewire.

The second electrode pad 166 may serve to reflect light. Thus, as thesecond electrode pad 166 gets closer to the semiconductor structure 120,it is possible to enhance light extraction efficiency.

The convex portion of the second electrode pad 166 may be higher thanthe active layer 126. Accordingly, the second electrode pad 166 mayenhance light extraction efficiency and control an orientation angle byupwardly reflecting light emitted from the active layer 126 in adirection horizontal to the device.

The passivation layer 180 may be formed on top of and on the sidesurface of the semiconductor structure 120. The passivation layer 180may be in contact with the first insulation layer 131 in a regionadjacent to the second electrode 246 or in a lower portion of the secondelectrode 246.

An opening of the first insulation layer 131 where the second electrodepad 166 is in contact with a second conductive layer 150 may have awidth d22 ranging, for example, from 40 μm to 90 μm. When the width d22is less than 40 μm, the operating voltage may rise. When the width d22is greater than 90 μm, it may be difficult to secure a processing marginfor preventing exposure of the second conductive layer 150.

When the second conductive layer 150 is exposed outside the secondelectrode pad 166, there may be a reduction in reliability of thedevice. Accordingly, the width d22 may range from 60% to 95% of theentire width of the second electrode pad 166.

The first insulation layer 131 may electrically insulate the firstelectrode 142 from the active layer 126 and the second conductivesemiconductor layer 127. Also, the first insulation layer 131 mayelectrically insulate the second conductive layer 150 from the firstconductive layer 165.

The first insulation layer 131 may be made of at least one materialselected from a group consisting of SiO2, SixOy, Si3N4, SixNy, SiOxNy,Al₂O₃, TiO2, and AlN, but is not limited thereto. The first insulationlayer 131 may be formed as a single or multiple layers. For example, thefirst insulation layer 131 may be a distributed Bragg reflector (DBR)having a multi-layered structure including an Si oxide or a Ti compound.However, the present invention is not limited thereto, and the firstinsulation layer 131 may include various reflective structures.

When the first insulation layer 131 performs a reflection function, thefirst insulation layer 131 may upwardly reflect light emittedhorizontally from the active layer 126, thereby enhancing lightextraction efficiency. As the number of recesses 128 increases, anultraviolet semiconductor device may have more effective lightextraction efficiency than a semiconductor device that emits blue light.

The second conductive layer 150 may cover the second electrode 246.Accordingly, the second electrode pad 166, the second conductive layer150, and the second electrode 246 may form one electrical channel.

The second conductive layer 150 may cover the second electrode 246 andmay be in contact with the side surface and the bottom surface of thefirst insulation layer 131. The second conductive layer 150 may be madeof a material having high adhesion strength to the first insulationlayer 131 and may also be made of at least one material selected from agroup consisting of Cr, Al, Ti, Ni, and Au, or an alloy thereof. Thesecond conductive layer 150 may be made as a single or multiple layers.

A second insulation layer 132 may electrically insulate the secondconductive layer 150 from the first conductive layer 165. The firstconductive layer 165 may be electrically connected to the firstelectrode 142 through the second insulation layer 132.

The first conductive layer 165 and a junction layer 160 may be disposedaccording to the bottom surface of the semiconductor structure 120 andthe shape of the recesses 128. The first conductive layer 165 may bemade of a material with high reflectance. For example, the firstconductive layer 165 may contain aluminum. When the first conductivelayer 165 contains aluminum, the first conductive layer 165 may serve toupwardly reflect light emitted from the active layer 126, therebyenhancing light extraction efficiency.

The junction layer 160 may contain a conductive material. For example,the junction layer 160 may contain a material selected from a groupconsisting of gold, tin, indium, aluminum, silicon, silver, nickel, andcopper, or an alloy thereof.

A substrate 170 may be made of a conductive material. For example, thesubstrate 170 may contain a metal or a semiconductor material. Thesubstrate 170 may be made of a metal having good electrical conductivityand/or thermal conductivity. In this case, heat generated duringoperation of the semiconductor device may be quickly released to theoutside.

The substrate 170 may contain a material selected from a groupconsisting of silicon, molybdenum, tungsten, copper, and aluminum, or analloy thereof.

A square wave pattern may be formed on top of the semiconductorstructure 120. The square wave pattern may enhance the extractionefficiency for light emitted from the semiconductor structure 120. Thesquare wave pattern may have a different average height depending onultraviolet wavelengths. For UV-C, the average height ranges from 300 nmto 800 nm. When the height ranges from 500 nm to 600 nm, it is possibleto enhance light extraction efficiency.

FIGS. 2 and 3 are views illustrating a configuration in which opticaloutput power is enhanced depending on a change in number of recesses.

When the aluminum composition of the semiconductor structure 120increases, there may be a deterioration in electric current spreadingcharacteristics in the semiconductor structure 120. Also, the activelayer has a large amount of light emitted to the side than a GaN-basedblue light emitting device (TM mode). The TM mode may usually beperformed by an ultraviolet semiconductor device.

The ultraviolet semiconductor device has reduced electric currentspreading characteristics compared to a blue GaN semiconductor device.Accordingly, the ultraviolet semiconductor device needs to have arelatively large number of first electrodes 142 disposed thereincompared to the blue GaN semiconductor device.

When the aluminum composition increases, the electric current spreadingcharacteristics may deteriorate. Referring to FIG. 2 , electric currentis spread at only points adjacent to the first electrodes 142, and anelectric current density may rapidly decrease at points far from thefirst electrodes 142. Accordingly, an effective light emitting region P2may be narrowed.

The effective light emitting region P2 may be defined as a region fromthe center of the first electrode 142 having the highest electriccurrent density to a boundary having an electric current density of 40%or less. For example, the effective light emitting region P2 may beadjusted to be less than 40 μm from the center of each of the recesses128 depending on the level of injected electric current and the aluminumcomposition.

A low electric current density region P3 may have a low electric currentdensity and thus may hardly contribute to light emission. Therefore,according to an embodiment, it is possible to enhance the optical outputpower by placing a larger number of first electrodes 142 in the lowelectric current density region P3, which has a low electric currentdensity, or by using a reflective structure.

Generally, since a GaN-based semiconductor layer that emits blue lighthas relatively good electric current spreading characteristics, it ispreferable that the areas of the recesses 128 and the first electrodes142 be minimized. This is because the area of the active layer 126decreases as the areas of the recesses 128 and the first electrodes 142increase. However, according to an embodiment, the electric currentspreading characteristics are relatively low because the aluminumcomposition is high. Accordingly, it may be preferable to reduce the lowelectric current density region P3 by increasing the number of firstelectrodes 142 although this reduces the area of the active layer 126.

Referring to FIG. 3 , when the number of recesses 128 is 48, therecesses 128 may be arranged in a zigzag form instead of beingstraightly arranged in a horizontal or vertical direction. In this case,the area of the low electric current density region P3 may be furtherdecreased, and thus most of the active layer 126 may participate inlight emission.

When the number of recesses 128 ranges from 70 to 110, electric currentmay be efficiently spread, and thus it is additionally possible to lowerthe operating voltage and enhance the optical output power. For asemiconductor device that emits UV-C light, when the number of recesses128 is less than 70, electrical and optical characteristics may bedeteriorated. When the number of recesses 128 is greater than 110, it ispossible to enhance electrical characteristics, but there may be adeterioration in optical characteristics due to the reduction in volumeof the active layer. In this case, each of the recesses 128 may have adiameter ranging from 20 μm to 70 μm.

Referring to FIGS. 1 and 2 , a first area of where the plurality offirst electrodes 142 are in contact with the first conductivesemiconductor layer 124 may range from 7.4% to 20% or from 10% to 20% ofthe maximum horizontal sectional area of the semiconductor structure120. The first area may indicate the sum of areas of where the firstelectrodes 142 are in contact with the first conductive semiconductorlayer 124.

When the first area of the plurality of first electrodes 142 is lessthan 7.4%, electric current spreading characteristics cannot besufficient, and thus the optical output power decreases. When the firstarea is greater than 20%, the areas of the active layer 126 and thesecond electrode 246 excessively decrease, and thus the operatingvoltage increases and the optical output power decreases.

Also, the total area of the plurality of recesses 128 may range from 10%to 30% or from 13% to 30% of the maximum horizontal sectional area ofthe semiconductor structure 120. When the total area of the recesses 128does not fall within this range, it may be difficult to keep the totalarea of the first electrode 142 within the range of 7.4% to 20%. Also,there are an increase in operating voltage and a decrease in opticaloutput power.

The area of the second conductive semiconductor layer 127 may be equalto the maximum horizontal area of the semiconductor structure 120 minusthe total area of the recesses 128. For example, the area of the secondconductive semiconductor layer 127 may range from 70% to 90% of themaximum horizontal area of the semiconductor structure 120.

A second area of where the second electrode 246 and the secondconductive semiconductor layer 127 are in contact with each other mayrange from 50% to 70% of the maximum horizontal sectional area of thesemiconductor structure 120. The second area may be the total area ofwhere the second electrode 246 is in contact with the second conductivesemiconductor layer 127.

When the second area is less than 50%, the area of the second electrode246 is so small that there may be an increase in operating voltage and adecrease in hole injection efficiency. When the second area exceeds 70%,the first area cannot be effectively widened, and thus there may be adecrease in electron injection efficiency. An area of the secondelectrode 246 and the second conductive semiconductor layer 127 beingnot in contact with each other may range from 1% to 20%.

The first area is inversely proportional to the second area. That is,when the number of recesses 128 is increased to increase the number offirst electrodes 142, the area of the second electrode 246 decreases.Accordingly, in order to increase electrical and opticalcharacteristics, the spreading characteristics for electrons and holesshould be balanced. Accordingly, it is important to determine anappropriate ratio between the first area and the second area.

The ratio of the first area of where the plurality of first electrodes142 are in contact with the first conductive semiconductor layer 124 tothe second area of where the second electrode 246 is in contact with thesecond conductive semiconductor layer 127 (first area:second area) mayrange from 1:3 to 1:7.

When the area ratio is greater than 1:7, the first area is so relativelysmall that the electric current spreading characteristics maydeteriorate. Also, when the area ratio is less than 1:3, the second areais so relatively small that the electric current spreadingcharacteristics may deteriorate.

The first electrode 142 may contain a metal or metal oxide with lowresistance. The first electrode 142 may absorb visible light andultraviolet light. Accordingly, it is necessary to reduce the amount oflight absorbed by the first electrode 142 in terms of light extraction.

For example, when the first electrode 142 is narrowed and a reflectivelayer is disposed, it is possible to enhance the light extractionefficiency. In this case, it is important to secure a maximum reflectiveregion while securing the contact area of the first electrode 142 neededto spread electric current.

FIG. 4 is an enlarged view of a part A of FIG. 1 , FIG. 5 is an enlargedview of a part B of FIG. 3 , FIG. 6 is an enlarged view of a part C ofFIG. 4 , and FIG. 7 is a diagram showing a layer structure of a firstelectrode and a reflective layer.

Referring to FIG. 4 , the first conductive semiconductor layer 124 mayhave a low concentration layer 124 a having a relative low aluminumconcentration and a high concentration layer 124 b having a relativehigh aluminum concentration. The aluminum concentration of the highconcentration layer 124 b may range from 60% to 70%, and the aluminumconcentration of the low concentration layer 124 a may range from 40% to50%. The low concentration layer 124 a may be disposed adjacent to theactive layer 126.

The first electrode 142 may be disposed inside the low concentrationlayer 124 a. That is, the recess 128 may be formed even in the region ofthe low concentration layer 124 a. This is because the highconcentration layer 124 b has a high aluminum concentration and relativelow electric current spreading characteristics. Accordingly, the firstelectrode 142 may be in contact with and thus ohmic with the lowconcentration layer 124 a inside the recess 128, and light emitted tothe high concentration layer 124 b is not absorbed by the highconcentration layer 124 b, and thus it is possible to enhance the lightemitting efficiency.

The recess 128 may have a diameter W3 ranging from 20 μm to 70 μm. Thediameter W3 of the recess 128 may be the diameter of a region of therecess 128 formed under the second conductive semiconductor layer 127and having the greatest area.

The diameter W1 of the recess 128 is less than 20 μm, it is difficult tosecure a processing margin for forming the first electrode 142 disposedinside the recess 128. Also, the diameter W1 of the recess 128 isgreater than 70 μm, the area of the active layer 126 may decrease andthus the light emission efficiency may deteriorate.

The recess 128 may have a diameter W5 of a top surface 128-1 rangingfrom 25 μm to 65 μm. For example, the diameter W3 of the recess 128 maybe 56 μm, and the diameter W5 of the top surface 128-1 may be 54 μm. Therecess 128 may have an incline angle θ5 ranging from 70 degrees to 90degrees. When this range is satisfied, this is advantageous in formingthe first electrode 142 on the top surface 128-1, and it is possible toform a large number of recesses 128.

When the incline angle θ5 is less than 90 degrees or greater than 120degrees, the area of the active layer 126 may decrease and thus thelight emission efficiency may deteriorate. It is possible to adjust thearea of the first electrode 142 and the area of the second electrode 246by using the incline angle θ5 of the recess 128.

In order to reduce absorption of ultraviolet light, the second electrode246 may have a smaller thickness than the first insulation layer 131.The thickness of the second electrode 246 may range from 1 nm to 15 nm.

The second electrode 246 and the first insulation layer 131 may have aseparation distance S4 ranging from 1 μm to 4 μm. When the separationdistance S4 is less than 1 μm, it is difficult to secure a processingmargin and thus there may be a reduction in reliability. When theseparation distance S4 is greater than 4 μm, the area of the secondelectrode 246 is small so that the operative voltage may increase.

The second conductive layer 150 may cover the second electrode 246.Accordingly, the second electrode pad 166, the second conductive layer150, and the second electrode 246 may form one electrical channel.

When the second conductive layer 150 is in contact with the side surfaceand the bottom surface of the first insulation layer 131, it is possibleto enhance thermal and electrical reliability of the second electrode246. Also, the second conductive layer 150 may have a reflectionfunction for upwardly reflecting light emitted to a gap between thefirst insulation layer 131 and the second electrode 246. A region wherea Schottky junction is formed by the second conductive semiconductorlayer 126 coming into contact with the second conductive layer 150 maybe disposed. By forming the Schottky junction, it is possible tofacilitate spreading of electric current.

The second conductive layer 150 may extend to a lower portion of thefirst insulation layer 131. In this case, it is possible to suppressdetachment of an end portion of the first insulation layer 131.Accordingly, it is possible to prevent penetration of external moistureor contaminants.

The second insulation layer 132 may electrically insulate the secondconductive layer 150 from the first conductive layer 165. The firstconductive layer 165 may be electrically connected to the firstelectrode 142 through the second insulation layer 132.

According to an embodiment, the second insulation layer 132 is disposedbetween the first electrode 142 and the second electrode 246 and overthe first insulation layer 131, and thus it is possible to preventpenetration of external moisture and/or other contaminants even when adefect occurs in the first insulation layer 131.

For example, when the first insulation layer 131 and the secondinsulation layer 132 are formed as a single layer, a defect such as acrack may easily propagate in a thickness direction. Accordingly,external moisture or contaminants may penetrate into the semiconductorstructure through the exposed defect.

However, according to an embodiment, the second insulation layer 132 isseparately disposed on the first insulation layer 131, and thus it isdifficult for a defect formed in the first insulation layer 131 topropagate to the second insulation layer 132. That is, an interfacebetween the first insulation layer 131 and the second insulation layer132 may serve to block the propagation of the defect.

The first insulation layer 131 may have a smaller thickness than thesecond insulation layer 132. For example, the thickness of the firstinsulation layer 131 may range from 300 nm to 700 nm. When the thicknessis less than 300 nm, electrical reliability may deteriorate. When thethickness is greater than 700 nm and the second conductive layer 150 isdisposed on the top surface and side surface of the first insulationlayer 131, the second conductive layer 150 may have poor step coveragecharacteristics, thus causing a detachment or crack. When a detachmentor crack is caused, there may be a deterioration in the electricreliability or a reduction of the light extraction efficiency.

The thickness of the second insulation layer 132 may range from 400 nmto 1000 nm. When the thickness is less than 400 nm, electricalreliability may deteriorate when the device operates. When the thicknessis greater than 1000 nm, reliability may be reduced due to a pressure ora thermal stress applied to the device when the device is processed, andalso the cost of the device may increase due to a long processing time.The thicknesses of the first insulation layer 131 and the secondinsulation layer 132 are not limited thereto.

Referring to FIGS. 4 to 6 , the first electrode 142 electricallyconnected to the first conductive semiconductor layer 124 may bedisposed on the top surface 128-1 of the recess 128. A reflective layer162 may be disposed between the first electrode 142 and the firstconductive semiconductor layer 124 in a thickness direction of thesemiconductor structure. With such a configuration, it is possible toprevent light absorption in the semiconductor structure by reflectinglight L1 incident onto the first electrode 142.

A first groove 142-1 may be formed on a first surface of the firstelectrode 142. The reflective layer 162 may be formed in the firstgroove 142-1. The first groove 142-1 may be formed while the firstelectrode 142 is formed after the reflective layer 162 is formed.

The reflective layer 162 may be disposed on the top surface 128-1 of therecess 128 to be in direct contact with the first conductivesemiconductor layer 124. However, the present invention is not limitedthereto. As will be described below, the reflective layer 162 may bedisposed on the bottom of the first electrode 142 or disposed inside thefirst electrode 142.

The reflective layer 162 may be a diameter W1 ranging form 4 μm to 20μm. When the thickness W1 of the reflective layer 162 is less than 4 μm,light absorption of the first electrode 142 increases. When thethickness W1 of the reflective layer 162 is greater than 20 4 μm, it isdifficult to secure the area of the first electrode 142 for injectingelectric current.

The first electrode 142 may have a diameter W2 ranging from 24 μm to 50μm. When this range is satisfied, this is advantageous in spreadingelectric current, and it is possible to place a large number of firstelectrodes 142.

When the diameter W2 of the first electrode 142 is less than 24 μm,electric current injected into the first conductive semiconductor layer124 may not be sufficient. Also, when the diameter W2 of the firstelectrode 142 is greater than 50 μm, the number of first electrodes 142is so insufficient that the electric current spreading characteristicsmay be deteriorated.

The width S2 of the first electrode 142 may be a difference between aradius S1+S2 of the first electrode 142 and a radius S1 of thereflective layer 162. The width S2 of the first electrode 142 may rangefrom 5 μm to 20 μm.

The width S2 of the first electrode 142 is proportional to the aluminumcomposition of the first conductive semiconductor layer 124. Forexample, when the aluminum composition of the first conductivesemiconductor layer 124 is 60%, the width S2 of the first electrode 142may be 30 nm. On the other hand, when the aluminum composition of thefirst conductive semiconductor layer 124 is 40%, the width S2 of thefirst electrode 142 may be 10 nm. This is because the electric currentspreading efficiency deteriorates as the aluminum composition increases.

The ratio of the area of the reflective layer 162 to the area of thefirst electrode 142 may range from 1:2 to 1:4. That is, the area of thereflective layer 162 may range from 25% to 50% of the area of the firstelectrode 142. When the area ratio is less than 1:2, the area of thefirst electrode 142 is so small that the electric current spreadingefficiency may be reduced. Also, when the area ratio is greater than1:4, the area of the reflective layer 162 is so small that the amount oflight absorbed by the first electrode 142 may increase.

When the ratio of the first area of where the first electrode 142 is incontact with the first conductive semiconductor layer 124 to the secondarea of where the second electrode 246 is in contact with the secondconductive semiconductor layer 127 (first area:second area) ismaintained in a range from 1:3 to 1:7, it is possible to enhance theelectric current spreading characteristics and the light extractionefficiency.

Referring to FIG. 6 , the thickness d2 of the first electrode 142 may besmaller than the thickness d3 of the first insulation layer 131. Thethickness d3 of the first insulation layer 131 may be greater than orequal to 110% to 130% of the thickness d2 of the first electrode 142.When the thickness d2 of the first electrode 142 is smaller than thethickness d3 of the first insulation layer 131, it is possible to solvea problem such as a detachment or crack caused by a reduction of stepcoverage characteristics caused when the first conductive layer 165 isdisposed. Also, the first electrode 142 and the first insulation layer131 have a first distance S6 therebetween, and thus it is possible toenhance gap-fill characteristics of the second insulation layer 132.

The first distance S6 between the first electrode 142 and the firstinsulation layer 131 may be greater than 0 μm and less than 4 μm. Whenthe first distance S6 between the first electrode 142 and the firstinsulation layer 131 is greater than 4 μm, the width of the firstinsulation layer 131 disposed on the top surface 128-1 of the recess 128decreases so much that it may be difficult to secure a processingmargin, and thus there may be a deterioration in reliability. Also, thewidth S2 of the first electrode 142 decreases so much that the operatingvoltage characteristics may deteriorate.

The top surface 128-1 of the recess 128 may include a first region S5 inwhich the first insulation layer 131 is in contact with the firstconductive semiconductor layer 124, a second region (a first interval)S6 in which the second insulation layer 132 is in contact with the firstconductive semiconductor layer 124, a third region S2 in which the firstelectrode 142 is in contact with the first conductive semiconductorlayer 124, and a fourth region W1 in which the reflective layer 162 isin contact with the first conductive semiconductor layer 124.

The third region S2 may be narrowed as the first region S5 is widened,and the third region S2 may be widened as the first region S5 iswidened.

The first region S5 may have a width ranging from 11 μm to 28 μm in afirst direction (an X direction). When the first direction width is lessthan 11 μm, it is possible to secure a processing margin, and thus it ispossible for device reliability to deteriorate. When the first directionwidth is greater than 28 μm, the width S2 of the first electrode 142decreases so much that electrical characteristics may deteriorate. Thefirst direction may be a direction perpendicular to the thicknessdirection of the semiconductor structure.

The width of the second region S6 may be determined by adjusting thewidths of the third region S6 and the fourth region W1. In order touniformly spread electric current over the device and optimize injectionof electric current, the width of the recess 128 may be freely designedto be within the aforementioned range.

Also, the area of the top surface 128-1 of the recess 128 may bedetermined by adjusting the widths of the first region S5, the secondregion S6, and the third region S2. When the area of the recess 128increases, the area in the second electrode 246 may be disposeddecreases. Thus, the ratio of the first electrode 142 to the secondelectrode 246 may be determined, and the width of the recess 128 may bedesigned in the range in order to optimize an electric current densityby matching densities of electrons and holes.

Referring to FIG. 7 , the reflective layer 162 includes a first layer162 a and a second layer 162 b. The first layer 162 a may perform anadhesion function and a electric current spreading prevention function.The first layer 162 a may contain at least one of chromium (Cr),titanium (Ti), and nickel (Ni). The first layer 162 a may have athickness ranging from 0.7 m to 7 nm. When the thickness is less than0.7 m, an adhesive effect and a spreading prevention effect may bereduced. When the thickness is greater than 7 nm, ultraviolet lightabsorption may increase.

The second layer 162 b may contain aluminum. The second layer 162 b mayhave a thickness ranging from 30 nm to 120 nm. When the thickness of thesecond layer 162 b is less than 30 nm, reflectance is reduced in anultraviolet wavelength band. Even when the thickness is greater than 120nm, reflective efficiency hardly increases.

The first electrode 142 may be composed of a plurality of layers. Forexample, the first electrode 142 may include a 1-1 (first-prime)electrode 142 a, a 1-2 (first-double-prime) electrode 142 b, and a 1-3electrode 142 c. The 1-1 electrode 142 a may contain at least one ofchromium (Cr), titanium (Ti), and nickel (Ni). The 1-1 electrode 142 amay have a similar structure to the first layer 162 a, but may have alarger thickness than the first layer 162 a in terms of ohmicperformance. Accordingly, the first electrode 142 absorbs ultravioletlight.

The 1-2 electrode 142 b may serve to lower resistance or reflect light.The 1-2 electrode 142 b may contain Ni, Al, or the like. The 1-3electrode 142 c is a layer for bonding with a neighboring layer and maycontain Au or the like. The first electrode 142 may have a structure ofTi/AI or Cr/Ti/AI, but is not particularly limited.

FIG. 8A is a first modification of FIG. 5 , FIG. 8B is a secondmodification of FIG. 5 , FIG. 9 is a third modification of FIG. 5 , andFIG. 10 is a diagram showing various shapes of a reflective layer.

Referring to FIG. 8A, the reflective layer 162 may be disposed under thefirst electrode 142. In this case, the area of where the first electrode142 is in contact with the first conductive semiconductor layer 124increases, and thus this may be advantageous in spreading electriccurrent. Also, the reflective layer 162 may be disposed inside the firstelectrode 142.

Referring to FIG. 8B, a cover electrode 143 may be disposed to cover alower portion of the first electrode 142 inside the recess 128. Thecover electrode 143 may be made of a material that is the same as ordifferent from that of the first conductive layer 165.

The first insulation layer 131 may extend to the top surface of therecess 128 and may be disposed a first distance S6 from the firstelectrode 142. The cover electrode 143 may include an uneven portion 143a disposed in the first distance S6. Accordingly, it is possible tofacilitate spreading of electric current by forming a Schottky junctionbetween the cover electrode 143 and the first conductive semiconductorlayer 124. Also, the cover electrode 143 may include an extension part143 b that extends to the lower portion of the first insulation layer.

Referring to FIG. 9 , the first conductive layer 165 may be connected toa reflective layer 162-1. The first conductive layer 165 may be broughtin contact with the reflective layer 162-1 via the first electrode 142.The first electrode 142 may have a ring shape in which a hole is formedat the center. Accordingly, the first conductive layer 165 may fill thehole of the first electrode 142 to form the reflective layer 162-1.

However, the present invention is not limited thereto. For example, thefirst electrode 142 may cover the reflective layer 162-1, and the firstconductive layer 165 may be connected to the reflective layer 162-1 viathe first electrode 142. In this case, the first conductive layer 165and the reflective layer 162-1 may be made of the same or differentmaterials.

The first conductive layer 165 may contain various materials capable ofultraviolet light, such as aluminum. The first conductive layer 165 mayextend to the bottom surface of the second conductive semiconductorlayer to reflect ultraviolet light. For example, the first conductivelayer 165 may be disposed to cover a region P1 in which the secondelectrode 246 is disposed.

Referring to FIG. 10 , the shape of the reflective layer 162 may bevariously modified. That is, the shape is not particularly limited aslong as a structure is capable of being disposed in a portion of thefirst electrode 142 to reflect light. However, as described above, thearea of the reflective layer 162 may be 25% to 50% of the area of thefirst electrode 142.

FIG. 11 is a conceptual view of a semiconductor device according toanother embodiment of the present invention.

Referring to FIG. 11 , a reflective pattern 247 may be disposed betweenthe second electrode 246 and the second conductive semiconductor layer127. The second electrode 246 may be relatively wider than the firstelectrode 142 and thus may have much light absorption. Furthermore, whenthe second conductive semiconductor layer 127 is made of P—AlGaN, mostlight may be incident onto the second electrode 246 through the secondconductive semiconductor layer 127. Accordingly, it is preferable thatlight absorbed by the second electrode 246 be minimized.

The above-described configuration of the reflective layer 162 of thefirst electrode 142 may be applied to the reflective pattern 247 as itis. For example, the reflective pattern 247 may have a structure throughwhich the second conductive layer 150 partially passes. However, thepresent invention is not limited thereto, and the reflective pattern 247may have a separate reflective member formed therein.

The reflective pattern 247 may have the reflective layer 162 formed onboth of the top surface 128-1 of the recess 128 and the lower surface ofthe second conductive semiconductor layer 127 by using a mask after therecess 128 is formed in the semiconductor structure. Accordingly, thereflective layer 162 disposed on the first electrode 142 and thereflective pattern 247 disposed on the second electrode 246 may have thesame composition and the same thickness. Subsequently, the firstelectrode 142 and the second electrode 246 may be disposed thereon.

The second electrode 246 may be disposed a certain distance W21+S7 fromthe center of the recess 128. The distance between the second electrode246 and the recess 128 may be adjusted according to the area of thefirst electrode 142 and the light extraction efficiency.

FIG. 12 is a sectional view of a semiconductor device according to athird embodiment of the present invention, FIG. 13A is an enlarged viewof a part A of FIG. 12 , and FIG. 13B is a modification of FIG. 13A.

Referring to FIGS. 12 and 13A, the semiconductor device according to thethird embodiment of the present invention includes a semiconductorstructure 120; a first insulation layer 131 disposed on thesemiconductor structure 120; a first electrode 151 disposed on a firstconductive semiconductor layer 124 through a first hole 171 a of thefirst insulation layer 131; a second electrode 161 disposed on a secondconductive semiconductor layer 127 through a second hole 171 b of thefirst insulation layer 131; a first cover electrode 152 disposed on thefirst electrode 151; a second cover electrode 164 disposed on the secondelectrode 161; and a second insulation layer 132 disposed on the firstcover electrode 152 and the second cover electrode 164.

The semiconductor structure 120 according to an embodiment of thepresent invention may output ultraviolet wavelength light. For example,the semiconductor structure 120 may output near-ultraviolet wavelengthlight (UV-A), far-ultraviolet wavelength light (UV-B), ordeep-ultraviolet wavelength light (UV-C).

When the semiconductor structure 120 emits ultraviolet wavelength light,each semiconductor layer of the semiconductor structure 120 may containa material having an empirical formula Inx1Aly1Ga1-x1-y1N (0≤x1≤1,0<y1≤1, 0≤x1+y1≤1) such as Al. Here, an aluminum composition may berepresented as the ratio of the atomic weight of Al to the total atomicweight including the atomic weight of In, the atomic weight of Ga, andthe atomic weight of Al. For example, when the aluminum composition is40%, the material may be Al40Ga60N, which has a gallium composition of60%.

Also, in the description of the embodiments, a composition being low orhigh may be understood by a difference in composition % (and/or % point)of each semiconductor layer. For example, when the first semiconductorlayer has an aluminum composition of 30% and the second semiconductorlayer has an aluminum composition of 60%, the aluminum composition ofthe second semiconductor layer may be represented as being higher thanthat of the first semiconductor layer by 30%.

A substrate 110 may be formed of a material selected from among sapphire(Al₂O₃), SiC, GaAs, GaN, ZnO, Si, GaP, InP, and Ge, but is not limitedthereto. The substrate 110 may be a light transmitting plate capable oftransmitting ultraviolet wavelength light.

A buffer layer 111 may mitigate a lattice mismatch between the substrate110 and semiconductor layers. The buffer layer 111 may have a form inwhich a group III element and a group V element are combined with eachother or may contain any one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN,and AlInN. In this embodiment, the buffer layer 111 may be AlN, but isnot limited thereto. The buffer layer 111 may include a dopant, but isnot limited thereto.

The configurations described with reference to FIG. 1 may be included asthe configurations of the first conductive semiconductor layer 124, theactive layer 126, and the second conductive semiconductor layer 127.

The first insulation layer 131 may be disposed between the firstelectrode 151 and the second electrode 161. In detail, the firstinsulation layer 131 may include a first hole 171 a in which the firstelectrode 151 is disposed and a second hole 171 b in which the secondelectrode 161 is disposed.

The first electrode 151 is disposed on the first conductivesemiconductor layer 124, and the second electrode 161 may be disposed onthe second conductive semiconductor layer 127.

Each of the first electrode 151 and the second electrode 161 may be anohmic electrode. Each of the first electrode 151 and the secondelectrode 161 may be made of at least one of indium tin oxide (ITO),indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminumzinc oxide (IAZO), indium gallium zinc oxide (IGZO), indium gallium tinoxide (IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO),gallium zinc oxide (GZO), IZO nitride (IZON), Al—Ga ZnO (AGZO), In—GaZnO (IGZO), ZnO, IrOx, RuOx, NiO, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO,Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, Mg, Zn, Pt, Au, and Hf, butis not limited thereto. For example, the first electrode 151 may have aplurality of metal layers (e.g., Cr, Al, and Ni), and the secondelectrode 161 may be made of ITO.

The first electrode 151 may be electrically connected with the firstconductive semiconductor layer 124 via the first hole 171 a. The firstelectrode 151 may include a first groove 151 a formed on one surface.For an ultraviolet light emitting device unlike typical visible lightemitting devices, it is necessary to perform heat treatment on anelectrode at high temperature for ohmic operation. For example, heattreatment may be performed on the first electrode 151 and/or the secondelectrode at a temperature ranging from about 600° C. to about 900° C.In this process, an oxide film Ox1 may be formed on the surface of thefirst electrode 151. The oxide film Ox1 may act as a resistance layer,and thus the operating voltage may increase.

The oxide film Ox1 may be formed by oxidizing a material constitutingthe first electrode 151. Accordingly, when components such as theconcentration and/or the mass percentage of the material constitutingthe first electrode 151 are not constant or non-uniform heat is appliedto the surface of the first electrode 151 by other elements while heattreatment is performed on the first electrode 151, the thickness of theoxide film Ox1 may be non-uniformly formed.

Accordingly, the first electrode 151 according to an embodiment may havethe first groove 151 a formed on one surface to remove the oxide filmOx1. In this process, a protrusion portion 151 b surrounding the firstgroove 151 a may be formed.

While heat treatment is performed on the first electrode 151, at least aportion of the side surface of the first conductive semiconductor layer124, the side surface of the active layer 126, and the side surface ofthe second conductive semiconductor layer 127, which is exposed betweenthe first electrode 151 and the second electrode 161, may be oxidized orcorroded.

However, according to an embodiment, the first insulation layer 131 mayextend from a portion of the top surface of the second conductivesemiconductor layer 127 and may be disposed even in the side surface ofthe active layer 126 and a portion of the first conductive semiconductorlayer 124. Also, the first insulation layer 131 may be disposed betweenthe first electrode 151 and the second electrode 161 and on the sidesurface of the first conductive semiconductor layer 124, the sidesurface of the active layer 126, and the side surface of the secondconductive semiconductor layer 127.

Accordingly, by using the first insulation layer 131, it is possible toprevent at least a portion of the side surfaces of the first conductivesemiconductor layer 124, the active layer 126, and the second conductivesemiconductor layer 127 from being corroded while heat treatment isperformed on the first electrode 151.

When the first electrode 151 is entirely etched, even the firstinsulation layer 131 disposed adjacent to the first electrode 151 may beetched. Therefore, according to an embodiment, the protrusion portion151 b may be formed by etching only a portion of the first electrode 151to leave a border region. The protrusion portion 151 b may have an upperwidth d3 ranging from 1 um to 10 um. When the width d3 is greater thanor equal to 1 um, it is possible to prevent the first insulation layer131 from being etched. When the width d3 is less than or equal to 10 um,the area of the first groove increases, and a region in which the oxidefilm has been removed increases. Thus, it is possible to reduce asurface area acting as resistance.

For example, when the first groove 151 a is formed in a portion of thefirst electrode 151, a mask composed of a photoresist may be disposed byplacing the photoresist and performing an exposure process. The mask mayhave an incline angle of a side surface positioned between an uppersurface and a lower surface with respect to the bottom surface of thesubstrate. Accordingly, since even a portion of the protrusion portion151 b of the first electrode 151 may be etched by adjusting the inclineangle of the mask, the thickness of the oxide film Ox1 formed on theprotrusion portion 151 b may be non-uniform. Depending on the case, theprotrusion portion 151 b of the first electrode 151 and the oxide filmleft on the side surface may be partially removed.

The first cover electrode 152 may be disposed on the first electrode151. In this case, the first cover electrode 152 may include a firstuneven portion 152 a disposed on the first groove 151 a. According tosuch a configuration, it is possible to improve an electrical connectionbetween the first cover electrode 152 and the first electrode 151 andthus also possible to lower the operating voltage. When no first groove151 a is present in the first electrode 151, the oxide film is notremoved, and thus resistance between the first cover electrode 152 andthe first electrode 151 may increase.

The first cover electrode 152 may cover the side surface of the firstelectrode 151. Accordingly, the area of where the first cover electrode152 and the first electrode 151 are in contact with each other iswidened, and thus it is possible to further lower the operating voltage.Also, since the first cover electrode 152 covers the side surface of thefirst electrode 151, it is possible to protect the first electrode 151from external moisture or contaminants. Accordingly, it is possible toimprove reliability of the semiconductor device.

The first cover electrode 152 may include a second uneven portion 152 bdisposed in a separation region d2 between the first insulation layer131 and the first electrode 151. The second uneven portion 152 b may bein direct contact with the first conductive semiconductor layer 124.Also, when the first cover electrode 152 is in direct contact with thefirst conductive semiconductor layer 124, resistance between the firstcover electrode 152 and the first conductive semiconductor layer 124 isgreater than the resistance between the first electrode 151 and thefirst conductive semiconductor layer 124. Accordingly, advantageously,it is possible to uniformly spread electric current injected into thefirst conductive semiconductor layer 124. The separation region d2 mayhave a width ranging from about 1 um to about 10 um.

The first cover electrode 152 may have a first region d1 extending anupper portion of the first insulation layer 131. Accordingly, the entirearea of the first cover electrode 152 increases, and thus it is possibleto lower the operating voltage.

When the first cover electrode 152 does not extend to the upper portionof the first insulation layer 131, an edge of the first insulation layer131 may be detached and thus separated from the first conductivesemiconductor layer 124. Accordingly, external moisture and/or othercontaminants may enter the gap. As a result, at least a portion of theside surface of the first conductive semiconductor layer 124, the sidesurface of the active layer 126, and the side surface of the secondconductive semiconductor layer 127 may be corroded or oxidized.

In this case, the ratio of the entire area of the second region d2 tothe entire area of the first region d1 (d4:d1) may range from 1:0.15 to1:1. The entire area of the first region d1 may be smaller than theentire area of the second region d2. Here, the second region d2 may be aregion where the first insulation layer 131 is disposed between thefirst and second electrodes 151 and 161 and over the first conductivesemiconductor layer 124.

When the entire area ratio d4:d1 is greater than or equal to 1:0.15, thearea of the first region d1 may increase to cover the upper portion ofthe first insulation layer 131, thereby preventing a detachment. Also,by the first insulation layer 131 being disposed between the firstelectrode 151 and the second electrode 161, it is possible to preventpenetration of external moisture or contaminants.

Also, when the entire area ratio d1:d4 is less than or equal to 1:1, itis possible to secure the area of the first insulation layer 131 tosufficiently cover a region between the first electrode 151 and thesecond electrode 161. Accordingly, it is possible to prevent thesemiconductor structure from being corroded when heat treatment isperform on the first electrode 151 and/or the second electrode 161.

The second cover electrode 164 may be disposed on the second electrode161. The first cover electrode 152 may cover even the side surface ofthe second electrode 161, but is not limited thereto.

The first cover electrode 152 and the second cover electrode 164 maycontain at least one of Ni/Al/Au, Ni/IrOx/Au, Ag, Ni, Cr, Ti, Al, Rh,Pd, Ir, Sn, In, Ru, Mg, Zn, Pt, Au, and Hf, but are not particularlylimited. However, the first cover electrode 152 and the second coverelectrode 164 may each have an exposed outermost layer containing Au.

The second insulation layer 132 may be disposed on the first coverelectrode 152, the second cover electrode 164, and the first insulationlayer 131. The second insulation layer 132 may include a third hole 153exposing the first cover electrode 152 and a fourth hole 163 exposingthe second cover electrode 164.

According to an embodiment, the second insulation layer 132 is disposedbetween the first electrode 151 and the second electrode 161 and overthe first insulation layer 131, and thus it is possible to preventpenetration of external moisture and/or other contaminants even when adefect occurs in the first insulation layer 131.

For example, when the first insulation layer and the second insulationis configured as a single layer, a defect such as a crack may easilypropagate in a thickness direction. Accordingly, external moisture orcontaminants may penetrate into the semiconductor structure through theexposed defect.

However, according to an embodiment, the second insulation layer 132 isseparately disposed on the first insulation layer 131, and thus it isdifficult for a defect formed in the first insulation layer 131 topropagate to the second insulation layer 132. That is, an interfacebetween the first insulation layer 131 and the second insulation layer132 may serve to block the propagation of the defect. Accordingly, it ispossible to prevent at least a portion of the side surface of the firstconductive semiconductor layer 124, the side surface of the active layer126, and the side surface of the second conductive semiconductor layer127 from being corroded or oxidized by external moisture and/or othercontaminants. Accordingly, it is possible to improve reliability of thesemiconductor device. In this case, when the first insulation layer 131and the second insulation layer 132 are made of different materials, itis possible to effectively prevent penetration of moisture orcontaminants. This is because when the first insulation layer 131 andthe second insulation layer 132 are deposited as different thin films,internal defects are not connected to each other in a direction of thedeposition (defect decoupling).

The first insulation layer 131 and the second insulation layer 132 maybe formed of at least one material selected from a group consisting ofSiO2, SixOy, Si3N4, SixNy, SiOxNy, Al₂O₃, TiO2, and AlN. A boundarybetween the first insulation layer 131 and the second insulation layer132 may partially disappear in a process of forming the secondinsulation layer 132.

Additionally, a first bump electrode 181 (see FIG. 20 ) may be disposedon the first cover electrode 152, and a second bump electrode 182 (seeFIG. 20 ) may be disposed on the second cover electrode 164. However,the present invention is not limited thereto. The first bump electrodeand the second bump electrode may be formed when a chip is mounted on acircuit board.

Referring to FIG. 13B, the semiconductor structure 120 may include astepped portion 211 extending from the upper surface of the firstconductive semiconductor layer 124 where the first electrode 151 isdisposed even to the upper surface of the second conductivesemiconductor layer 127 where the second electrode 161 is disposed. Thestepped portion 211 may be a first surface of the semiconductorstructure 120 including an inclined surface 212 formed by mesa etching,but is not limited thereto.

In this case, the first insulation layer 131 may be disposed on thefirst surface 211 apart from the first electrode 151, and the firstinsulation layer 131 may overlap with the first cover electrode 152 onthe first surface in the first direction perpendicular to the topsurface of the first conductive semiconductor layer.

In detail, the stepped portion 211 may include a first part E11 wherethe first electrode 151 is disposed, a second part E12 when the secondelectrode 161 is disposed, a third part E13 where the first insulationlayer 131 is disposed between the first part E11 and the second partE12, and a fourth part E14 where the first cover electrode 152 isdisposed between the first part E11 and the third part E13.

The third part E13 may include a 3-1 part E13-1 overlapping with thefirst cover electrode 152 in the first direction (the Y direction)perpendicular to the top surface of the first conductive semiconductorlayer 124. In this case, the 3-1 part E13-1 may have a width greaterthan 0 μm and less than 4 μm in the second direction (the X direction)perpendicular to the first direction. The third part E13 may be the sameregion as the above-described first distance S6.

Also, according to an embodiment, the stepped portion 211 may include afifth part E15 where the second cover electrode 164 is disposed betweenthe second part E12 and the third part E13 and a 3-1 part E13-2overlapping with the second cover electrode 164 in the first direction.That is, like the first cover electrode 152, the second cover electrode164 may extend to the upper portion of the first insulation layer 131,and it is possible to improve moisture resistance.

According to an embodiment, like the first electrode 151, the secondelectrode 161 may have a groove 161 a formed on the top surface.Accordingly, it is possible to decrease contact resistance between thesecond cover electrode 164 and the second electrode 161.

FIG. 14A is a plan view of the semiconductor device according to thethird embodiment of the present invention, FIG. 14B is a plan viewshowing an etching region of a first electrode according to the thirdembodiment of the present invention, FIG. 14C is a modification of FIG.14B, FIG. 14D is a plan view showing a first cover electrode and asecond cover electrode according to the third embodiment of the presentinvention, and FIG. 14E is a modification of FIG. 14D.

Referring to FIG. 14A, the first cover electrode 152 may be exposedthrough the third hole 153 of the second insulation layer 132, and thesecond cover electrode 164 may be exposed through the fourth hole 163 ofthe second insulation layer 132. The fourth hole 163 may have a shapecorresponding to the second cover electrode 164, and third hole 153 mayhave a quadrangular shape and may be disposed in a third partitionregion among a plurality of partition regions, which will be describedbelow. FIG. 12 is a sectional view taken along A-A of FIG. 14A.

Referring to FIG. 14B, the semiconductor structure may include aplurality of partition regions P1, P2, P3, and P4 that are defined by afirst virtual line L1 passing through the centers of a first sidesurface S1 and a third side surface S3 which are opposite to each otherand a second virtual line L2 passing through the centers of a secondside surface S2 and a fourth side surface S4 which are opposite to eachother, when viewed from the top. The first virtual line L1 and thesecond virtual line L2 may be perpendicular to each other, but are notlimited thereto.

In this case, the plurality of partition regions P1, P2, P3, and P4 mayinclude the first partition region P1 including the first side surfaceS1 and the fourth side surface S4, the second partition region P2including the first side surface S1 and the second side surface S2, thethird partition region P3 including the second side surface S2 and thethird side surface S3, and a fourth partition region P4 including thethird side surface S3 and the fourth side surface S4.

The first groove 151 a may include a 1-1 groove 151 a-1 disposed in thefirst partition region P1, a 1-2 groove 151 a-2 disposed in the secondpartition region P2, a 1-3 groove 151 a-3 disposed in the thirdpartition region P3, and a 1-4 groove 151 a-4 disposed in the fourthpartition region P4.

That is, the plurality of first grooves 151 a may be disposed apart fromeach other. In order to lower the operating voltage of the semiconductordevice, it is advantageous to increase the area of the second electrode.Accordingly, the space is narrowed, and thus the first grooves 151 a mayhave the form of islands spaced apart from each other. In this case, theprotrusion portion 151 b may have a structure surrounding the 1-1, 1-2,1-3, and 1-4 grooves 151 a-1, 151 a-2, 151 a-3, and 151 a-4.

In this case, a light emitting region and a second electrode are notdisposed in the third partition region P3, and thus the 1-3 groove 151a-3 may have a larger area than the 1-1 groove 151 a-1, the 1-2 groove151 a-2, and the 1-4 groove 151 a-4.

Referring to FIG. 14C, the plurality of grooves are connected to form asingle first groove 151 a. A protrusion portion may include a firstprotrusion line disposed inside the first groove 151 a (an inner line151 b-1) and a second protrusion line disposed outside the first groove151 a (an outer line 151 b-2). According to such a configuration, aregion in which an oxide film has been removed increases, and thus it ispossible to lower the operating voltage.

Referring to FIG. 14D, the second cover electrode 164 may include aplurality of pad parts 164 a-1, 164 a-2, and 164 a-3 and connectionparts configured to connect the plurality of pad parts 164 b-1 and 164b-2. The second cover electrode 164 may have the shape of a dumbbell,but is not limited thereto. The plurality of pad parts 164 a-1, 164 a-2,and 164 a-3 may have a circular shape. However, the present invention isnot limited thereto, and the plurality of pad parts 164 a-1, 164 a-2,and 164 a-3 may have various shapes.

The plurality of pad parts 164 a-1, 164 a-2, and 164 a-3 may include thefirst pad part 164 a-1 disposed in the first partition region P1, thesecond pad part 164 a-2 disposed in the second partition region P2, andthe third pad part 164 a-3 disposed in the fourth partition region P4.

The connection parts 164 b-1 and 164 b-2 may include the firstconnection part 164 b-1 connecting the first pad part 164 a-1 and thesecond pad part 164 a-2 and the second connection part 164 b-2connecting the second pad part 164 a-2 and the third pad part 164 a-3.In this case, the plurality of pad parts may be defined as circularregions, and the connection parts 164 b-1 and 164 b-2 may be defined asthe remaining regions that connect the pad parts 164 a-1, 164 a-2, and164 a-3 having a circular shape.

In this case, the first connection part 164 b-1 may have a widthdecreasing toward the first virtual line L1, and the second connectionpart 164 b-2 may have a width decreasing toward the second virtual lineL2. That is, the first connection part 164 b-1 may have the smallestwidth at the center point between the first pad part 164 a-1 and thesecond pad part 164 a-2 which are adjacent to the first connection part164 b-1.

According to such a configuration, the second cover electrode 164 has anincreased outer circumferential surface, and it is possible to provide aspace where a first groove is to be formed outside the connection part.Also, the light emitting region has an increased outer circumferentialsurface, and the probability that light will be emitted increases. Thus,it is possible to improve optical output power. Also, it is possible toform a plurality of pad parts. The ultraviolet light emitting deviceaccording to an embodiment generates more heat than visible lightemitting devices. Thus, it is possible to increase heat dissipationefficiency by having a plurality of bump pads.

The ratio of the area of the first partition region P1 to the area ofthe second cover electrode 164 disposed in the first partition region P1may range from 1:0.2 to 1:0.5. The area of the second cover electrode164 disposed in the first partition region P1 may be the same as thearea of the first pad part 164 a-1 and the second connection part 164b-2 disposed in the first partition region P1.

When the area ratio is greater than or equal to 1:0.2, the area of thesecond cover electrode 164 increases, and thus it is possible to improvehole injection efficiency. Also, the area of the first pad part 164 a-1increases, and thus the size of the bump electrodes may increase.Accordingly, it is possible to increase the heat dissipation efficiency.

When the area ratio is less than or equal to 1:0.5, the area of thefirst cover electrode 152 in the first partition region P1 increases,and thus it is possible to improve the hole injection efficiency. Also,it is possible to provide a space where a plurality of first grooves 151a will be formed outside the second cover electrode 164. Accordingly, itis possible to lower the operating voltage.

The ratio of the area of the second partition region P2 to the area ofthe second cover electrode 164 disposed in the second partition regionP2 may range from 1:0.2 to 1:0.5. Also, it like the ratio of the area ofthe third partition region P3 to the area of the second cover electrode164 disposed in the third partition region P3.

That is, according to an embodiment, the second cover electrodes 164disposed in the partition regions P1, P2, and P3 may have the same area.

The area ratio of the second cover electrode 152 to the first coverelectrode 164 may range from 1:1.1 to 1:1.15. That is, the area of thefirst cover electrode 152 may be larger than the area of the secondcover electrode 164. When the area ratio is greater than or equal to1:1.1, the area of the first cover electrode 152 increases, and thus itis possible to improve electron injection efficiency. Also, it ispossible to provide a space where a plurality of first grooves 151 awill be formed outside the second cover electrode 164. Accordingly, itis possible to lower the operating voltage.

When the area ratio is less than or equal to 1:1.15, the area of thesecond cover electrode 164 increases, and thus it is possible to improvethe hole injection efficiency. Also, the area of the pad partsincreases, and thus it is possible to increase the size of the bumpelectrodes. Accordingly, it is possible to increase the heat dissipationefficiency.

Referring to FIG. 14E, a shape for increasing the outer circumferentialsurface of the light emitting region may be variously modified. Thesecond cover electrode 164 may be formed in a shape corresponding to thelight emitting region. The second cover electrode 164 may include aplurality of second branch electrodes 164-1 extending in the X directionand a second connection electrode 164-2 connecting the plurality ofbranch electrodes 164-1.

The first cover electrode 152 may include a plurality of first branchelectrodes 152-1 disposed between the second branch electrodes 164-1 anda first connection electrode 152-2 connecting the plurality of firstbranch electrodes 152-1.

In this case, the ratio of the maximum perimeter of the light emittingregion to the maximum area of the light emitting region may range from0.02 [1/um] to 0.05 [1/um]. When the above condition is satisfied, theperimeter increases while the same area is remained, and thus it ispossible to increase the optical output power.

FIGS. 15 to 20 are plan views and sectional views showing a method ofmanufacturing the semiconductor device according to the third embodimentof the present invention.

Referring to FIGS. 15A and 15B, the first conductive semiconductor layer124, the active layer 126, and the second conductive semiconductor layer127 may be sequentially formed on the substrate 110. Subsequently, anon-light emitting region M2 where the first conductive semiconductorlayer 124 is exposed and a light emitting region M1 protruding over thenon-light emitting region M2 may be formed by mesa-etching thesemiconductor structure. Subsequently, the first insulation layer 131may be formed, and the first hole 171 a and the second hole 171 b may beformed. Accordingly, the first insulation layer 131 may usually bedisposed in a side surface of the light emitting region M1.

The mesa-etched light emitting region M1 may include a plurality ofcircular sections and a connection section connecting the plurality ofcircular sections when viewed from the top. According to such aconfiguration, a bumper pad may be disposed in each circular section,and thus it is possible to improve the heat dissipation efficiency.Since the semiconductor device according to an embodiment is anultraviolet light emitting device, the semiconductor device may be aGaN-based semiconductor material, which contains more aluminum thantypical visible light emitting devices. Accordingly, since much heat isgenerated by resistance, dissipation of the generated heat may be a bigissue.

At least a portion of the side surface of the second conductivesemiconductor layer 127, the side surface of the active layer 126, andthe side surface of the first conductive semiconductor layer 124 may beexposed in an inclined surface M3 between the light emitting region M1and the non-light emitting region M2. The semiconductor structureaccording to an embodiment contains much aluminum and thus may besusceptible to oxidization by moisture in the air or damage by othercontaminants. Accordingly, after the light emitting region M1 and thenon-light emitting region M2 are formed, the first insulation layer 131may be disposed in an inclined surface M3 therebetween to prevent damageof the inclined surface M3.

Referring to FIGS. 16A and 16B, the first electrode 151 may be formed onthe first conductive semiconductor layer 124. In detail, the firstelectrode 151 may be disposed in the first hole 171 a of the firstinsulation layer 131.

According to an embodiment, the first hole 171 a may have a larger areathan the bottom surface of the first electrode 151. For example, aseparation region d2 between the first electrode 151 and the firstinsulation layer 131 may have a distance ranging from 1 um to 10 um.

As the area of where the first electrode 151 is in contact with thefirst conductive semiconductor layer 124 increases, it is possible toimprove the electric current injection efficiency. When the separationdistance is greater than or equal to 1 um, it is possible to have aprocessing margin for securing the contact area in the area of the firstelectrode 151. Also, as described above, the first cover electrode 152may be disposed in the distance of the separation region d2 between thefirst electrode 151 and the first insulation layer 131. In order tosecure spreading characteristics of electric current injected into thewhole region of the semiconductor structure in consideration of theelectric current injection characteristics and the electric currentspreading characteristics, the distance of the separation region may beless than or equal to 10 um. Also, the first electrode 151 may bethicker than the first insulation layer 131.

Subsequently, as shown in FIGS. 17A and 17B, the second electrode 161may be formed in the light emitting region.

A typical method of forming an ohmic electrode may be applied to themethod of forming the first electrode 151 and the second electrode 161as it is. For example, the first electrode 151 may have a plurality ofmetal layers (e.g., Cr, Al, and Ni), and the second electrode 161 maycontain ITO. However, the present invention is not limited thereto.

Referring to FIGS. 18A and 18B, a step of etching the first electrode151 may be performed. According to this embodiment, since a deepultraviolet light emitting device has a higher aluminum composition thantypical visible light emitting devices, a heat treatment temperature ofthe electrode may increase. Accordingly, heat treatment may be performedat a temperature ranging from about 600 degrees to about 900 degrees inorder to improve ohmic characteristics between the semiconductorstructure and the first electrode 151 and/or the second electrode 161.In this heat treatment process, an oxide film may be formed on thesurface of the first electrode 151. Accordingly, it is possible toimprove an electrical connection with the cover electrode by etching thetop surface of the first electrode 151 to remove the oxide film.

Also, in the heat treatment process of the first electrode 151 and/orthe second electrode 161, the side surface of the first conductivesemiconductor layer 124 and/or the side surface of the active layer 126and/or the side surface of the second conductive semiconductor layer127, which are exposed between the light emitting region and thenon-light emitting region, may be oxidized or corroded. In order toprevent such a problem, the first insulation layer 131 may be disposedbetween the non-light emitting region and the light emitting region toprevent the side surface of the first conductive semiconductor layer 124and/or the side surface of the active layer 126 and/or the side surfaceof the second conductive semiconductor layer 127 from being oxidized orcorroded.

The semiconductor structure may include a plurality of partition regionsP1, P2, P3, and P4 that are defined by a first virtual line L1 passingthrough the centers of a first side surface S1 and a third side surfaceS3 which are opposite to each other and a second virtual line L2 passingthrough the centers of a second side surface S2 and a fourth surface S4which are opposite to each other, when viewed from the top. The firstvirtual line L1 and the second virtual line L2 may be perpendicular toeach other, but are not limited thereto.

In this case, the plurality of partition regions P1, P2, P3, and P4 mayinclude the first partition region P1 including the first side surfaceS1 and the fourth side surface S4, the second partition region P2including the first side surface S1 and the second side surface S2, thethird partition region P3 including the second side surface S2 and thethird side surface S3, and a fourth partition region P4 including thethird side surface S3 and the fourth side surface S4.

The first groove 151 a may include a 1-1 groove 151 a-1 disposed in thefirst partition region P1, a 1-2 groove 151 a-2 disposed in the secondpartition region P2, a 1-3 groove 151 a-3 disposed in the thirdpartition region P3, and a 1-4 groove 151 a-4 disposed in the fourthpartition region P4. That is, the plurality of first grooves 151 a maybe disposed apart from each other. In order to lower the operatingvoltage, it is advantageous to increase the area of the secondelectrode. Accordingly, the space is narrowed, and thus the firstgrooves 151 a may have the form of islands spaced apart from each other.In this case, the protrusion portion 151 b may have a structuresurrounding the 1-1, 1-2, 1-3, and 1-4 grooves 151 a-1, 151 a-2, 151a-3, and 151 a-4.

In this case, a light emitting region is not disposed in the thirdpartition region P3, and thus the 1-3 groove 151 a-3 may have a largerarea than the 1-1 groove 151 a-1, the 1-2 groove 151 a-2, and the 1-4groove 151 a-4.

Referring to FIGS. 19A and 19B, the first cover electrode 152 may bedisposed on the first electrode 151. The first cover electrode 152 maybe disposed on the first electrode 151. In this case, the first coverelectrode 152 may have a first groove disposed at one surface, and thefirst cover electrode 152 may include a first uneven portion 152 adisposed in the first groove 151 a. According to such a configuration,it is possible to improve an electrical connection between the firstcover electrode 152 and the first electrode 151 and thus also possibleto lower the operating voltage. When no first groove 151 a is present inthe first electrode 151, the oxide film is not removed, and thus theelectrical connection between the first cover electrode 152 and thefirst electrode 151 may be weakened.

The first cover electrode 152 may be widely formed to cover the sidesurface of the first electrode 151 and a portion of the first insulationlayer 131. The first cover electrode 152 may include a second unevenportion 152 b disposed in a separation region d2 between the firstinsulation layer 131 and the first electrode 151. The second unevenportion 152 b may be in direct contact with the first conductivesemiconductor layer 124. Accordingly, it is possible to enhance theelectric current injection efficiency.

The second cover electrode 164 may be disposed on the second electrode161. The first cover electrode 152 may cover even the side surface ofthe second electrode 161.

The first cover electrode 152 and the second cover electrode 164 maycontain at least one of Ni/Al/Au, Ni/IrOx/Au, Ag, Ni, Cr, Ti, Al, Rh,Pd, Ir, Sn, In, Ru, Mg, Zn, Pt, Au, and Hf, but are not limited thereto.However, the first cover electrode 152 and the second cover electrode164 may each have an exposed outermost layer containing Au.

Referring to FIGS. 20A, 20B, and 21 , the second insulation layer 132may be disposed on the first cover electrode 152, the second coverelectrode 164, and the first insulation layer 131. The second insulationlayer 132 may include a third hole 153 exposing the first coverelectrode 152 and a fourth hole 163 exposing the second cover electrode164.

In this case, the ratio of the area of the first cover electrode 152exposed by the third hole 153 to the area of the second cover electrode164 exposed by the fourth hole 163 may range from 1:2 to 1:5. When thearea ratio is greater than or equal to 1:2, the area of the second coverelectrode 164 increases, and it is possible to improve the holeinjection efficiency. Also, the area of the first pad part 164 a-1increases, and thus the size of the bump electrodes may increase.Accordingly, it is possible to increase the heat dissipation efficiency.When the area ratio is less than or equal to 1:5, the area of the firstcover electrode 152 increases, and thus it is possible to improve theelectron injection efficiency.

Additionally, a first bump electrode 181 may be disposed on the firstcover electrode 152, and a second bump electrode 182 may be disposed onthe second cover electrode 164. However, the present invention is notlimited thereto. The first bump electrode 181 and the second bumpelectrode 182 may be formed when a chip is mounted on a circuit board.

Referring to FIG. 22 , the first insulation layer 131 and the secondinsulation layer 132 may be formed of at least one material selectedfrom a group consisting of SiO2, SixOy, Si3N4, SixNy, SiOxNy, Al₂O₃,TiO2, and AlN. Also, the first insulation layer 131 and the secondinsulation layer 132 may be formed of the same material. Accordingly,the first insulation layer 131 and the second insulation layer 132 maybe formed of the same material on at least a portion of the side surfaceof the first conductive semiconductor layer 124, the side surface of theactive layer 126, and the side surface of the second conductivesemiconductor layer 127 located between the light emitting region andthe non-light emitting region. However, the present invention is notlimited thereto, and the first insulation layer 131 and the secondinsulation layer 132 may contain different materials.

The first insulation layer 131 may horizontally extend from a lowerportion of the second insulation layer 132 between the light emittingregion and the non-light emitting region and be disposed apart from thefirst electrode 151, and the first cover electrode 152 may be disposedon a portion of the first electrode 151 and the first insulation layer131. Thus, the first cover electrode 152 may be disposed between aportion of the first insulation layer 131 and a portion of the secondinsulation layer 132 to vertically overlap with the first insulationlayer 131 and the second insulation layer 132.

Referring to FIG. 23 , a semiconductor device 100 according to anembodiment may be mounted on a circuit board 10 as a flip chip. Thesemiconductor device 100 may include all of the above-describedelements. For example, the first bump electrode 181 and the second bumpelectrode 182 may be electrically connected to and mounted on electrodepads 11 and 12 of the circuit board 10. In this case, various fillingmembers 20 may be disposed between the semiconductor device 100 and thecircuit board 10. For example, each of the filling members may include amaterial capable of reflective ultraviolet light (e.g., aluminum).

FIG. 24 is a conceptual view of a semiconductor structure according toan embodiment of the present invention, and FIG. 25 is a graph obtainedby measuring an aluminum composition of FIG. 1 .

The semiconductor structure 120 according to an embodiment of thepresent invention may output ultraviolet wavelength light. For example,the semiconductor structure 120 may output near-ultraviolet wavelengthlight (UV-A), far-ultraviolet wavelength light (UV-B), ordeep-ultraviolet wavelength light (UV-C). The wavelength range may bedetermined by the aluminum composition of the semiconductor structure120.

Referring to FIG. 24 , a semiconductor device according to an embodimentincludes a semiconductor structure 120 including a first conductivesemiconductor layer 124, a second conductive semiconductor layer 127,and an active layer 126 disposed between the first conductivesemiconductor layer 124 and the second conductive semiconductor layer127.

The second conductive semiconductor layer 127 may include a 2-1(second-prime) conductive semiconductor layer 127 a having a highaluminum composition and a 2-2 (second-double-prime) conductivesemiconductor layer 127 b having a relatively low aluminum composition.

The second electrode 246 may be brought into ohmic contact with the 2-2conductive semiconductor layer 127 b. The second electrode 246 mayinclude a transparent electrode having relatively low ultraviolet lightabsorption. For example, the second electrode 246 may be formed of ITO,but is not limited thereto.

The second conductive layer 150 may inject electric current into thesecond conductive semiconductor layer 127. Also, the second conductivelayer 150 may reflect light emitted from the active layer 126.

According to an embodiment, the second electrode 246 may be in directcontact with a semiconductor layer (e.g., P—AlGaN) having a band gaplarger than energy of ultraviolet wavelengths. Conventionally, thesecond electrode 246 is disposed on a semiconductor layer (e.g., a GaNlayer) having a small band gap to facilitate an ohmic connection, andthus most ultraviolet light is absorbed by the GaN layer. However,according to an embodiment, the second electrode 246 is in direct ohmiccontact with P—AlGaN, and thus most light may pass through the secondconductive semiconductor layer 127.

However, there is absorption of ultraviolet light by most secondelectrodes. Accordingly, there is a need to improve light extractionefficiency while maintaining ohmic contact by the second electrode. Itis possible to improve light extraction efficiency while maintainingohmic characteristics by increasing light transmittance of the secondelectrode 246 and placing a conductive layer having reflectivecharacteristics on the lower portion of the second electrode 246.

Referring to FIG. 25 , an electron-blocking layer 129 may be disposedbetween the active layer 126 and the second conductive semiconductorlayer 127. The electron-blocking layer 129 may block electrons suppliedfrom the first conductive semiconductor layer 124 from flowing out tothe second conductive semiconductor layer 127, thus increasing theprobability that electrons and holes will be recombined with each otherin the active layer 126. The electron-blocking layer 129 may have ahigher energy band gap than the active layer 126 and/or the secondconductive semiconductor layer 127.

The electron-blocking layer 129 may be made of a material selected fromamong semiconductor materials having an empirical formulaInx1Aly1Ga1-x1-y1N (0≤x1≤1, and 0≤x1+y1≤1), for example, AlGaN, InGaN,InAlGaN, and so on, but is not limited thereto. A first layer 129 bhaving a high aluminum composition and a second layer 129 a having a lowaluminum composition may be alternately disposed in theelectron-blocking layer 129.

The first conductive semiconductor layer 124, the active layer includingthe barrier layer 126 b and the well layer 126 a, the 2-1 conductivesemiconductor layer 127 a, and the 2-2 conductive semiconductor layer127 b may all contain aluminum. Accordingly, the first conductivesemiconductor layer 124, the barrier layer 126 b, the well layer 126 a,the 2-1 conductive semiconductor layer 127 a, and the 2-2 conductivesemiconductor layer 127 b may be made of AlGaN. However, the presentinvention is not limited thereto.

The 2-1 conductive semiconductor layer 127 a may have a thicknessgreater than 10 nm and less than 200 nm. When the thickness of the 2-1conductive semiconductor layer 127 a is less than 10 nm, resistancethereof increases, and thus it is possible to reduce the electriccurrent injection efficiency. Also, when the thickness of the 2-1conductive semiconductor layer 127 a is greater than 200 nm, it ispossible to decrease crystallinity because of materials constituting the2-1 conductive semiconductor layer 127 a and thus improve electricalcharacteristics and optical characteristics.

The 2-1 conductive semiconductor layer 127 a may have a higher aluminumcomposition than the well layer 126 a. In order to generate ultravioletlight, the aluminum composition of the well layer 126 a may range fromabout 30% to about 50%. When the 2-1 conductive semiconductor layer 127a has a lower aluminum composition than the well layer 126 a, the 2-1conductive semiconductor layer 127 a absorbs light, and thus lightextraction efficiency may be reduced.

The aluminum composition of the 2-1 conductive semiconductor layer 127 amay be greater than 40% and less than 80%. When the aluminum compositionof the 2-1 conductive semiconductor layer 127 a is less than 40%, the2-1 conductive semiconductor layer 127 a absorbs light. When thealuminum composition of the 2-1 conductive semiconductor layer 127 a isgreater than 80%, electric current injection efficiency deteriorates.For example, when the aluminum composition of the well layer 126 a is30%, the aluminum composition of the 2-1 conductive semiconductor layer127 a may be 40%.

The 2-2 conductive semiconductor layer 127 b may have a lower aluminumcomposition than the well layer 126 a. When the 2-2 conductivesemiconductor layer 127 b has a higher aluminum composition than thewell layer 126 a, resistance between the second electrode and the 2-2conductive semiconductor layer 127 b increases, and thus electriccurrent may not be sufficiently injected.

The aluminum composition of the 2-2 conductive semiconductor layer 127 bmay be greater than 1% and less than 50%. When the aluminum compositionis greater than 50%, the 2-2 conductive semiconductor layer 127 b maynot be sufficiently ohmic with the second electrode. When the aluminumcomposition is less than 1%, the aluminum composition is almost a GaNcomposition, and thus the 2-2 conductive semiconductor layer 127 babsorbs light.

The 2-2 conductive semiconductor layer 127 b may have a thicknessgreater than about 1 nm and less than about 30 nm. As described above,the 2-2 conductive semiconductor layer 127 b has an aluminum compositionlow enough to be ohmic and thus may absorb ultraviolet light.Accordingly, it may be advantageous in terms of optical output power tocontrol the 2-2 conductive semiconductor layer 127 b to be as thin aspossible.

However, when the thickness of the 2-2 conductive semiconductor layer127 b is controlled to be 1 nm or less, the 2-2 conductive semiconductorlayer 127 b may not be disposed in some sections, and the 2-1 conductivesemiconductor layer 127 a may be partially exposed from thesemiconductor structure 120. Accordingly, it may be difficult for the2-2 conductive semiconductor layer 127 b to be formed as a single layerand also perform its role. Also, when the thickness is greater than 30nm, the amount of absorbed light is so large that optical output powerefficiency may decrease.

The 2-2 conductive semiconductor layer 127 b may include a 2-3conductive semiconductor layer 127 c and a 2-4 conductive semiconductorlayer 127 d. The 2-3 conductive semiconductor layer 127 c may be asurface layer in contact with the second electrode, and the 2-4conductive semiconductor layer 127 d may be a layer for adjusting thealuminum composition.

The 2-4 conductive semiconductor layer 127 d may be disposed between the2-1 conductive semiconductor layer 127 a having a relatively highaluminum content and the 2-3 conductive semiconductor layer 127 c havinga relatively low aluminum content. Accordingly, it is possible toprevent a deterioration of crystallinity due to a rapid change inaluminum content.

The aluminum composition of the 2-3 conductive semiconductor layer 127 cmay be greater than 1% and less than 20%. Alternatively, the aluminumcomposition may be greater than 1% and less than 10%.

When the aluminum composition is less than 1%, the 2-3 conductivesemiconductor layer 127 c may have a light absorption rate that is toohigh. When the aluminum composition is greater than 20%, contactresistance of the second electrode increases, and thus the electriccurrent injection efficiency may be reduced.

However, the present invention is not limited thereto, and the aluminumcomposition of the 2-3 conductive semiconductor layer 127 c may beadjusted in consideration of the electric current injectioncharacteristics and the light absorption rate. Alternatively, thealuminum composition may be adjusted according to optical output poweror electrical characteristics required by a product.

For example, when the electric current injection characteristics aremore important than the light absorption rate, the aluminum compositionmay be adjusted to be in the range of 1% to 10%. When the optical outputpower characteristics are more important than the electricalcharacteristics in products, the aluminum composition of the 2-3conductive semiconductor layer 127 c may be adjusted to be in the rangeof 1% to 20%.

When the aluminum composition of the 2-3 conductive semiconductor layer127 c is greater than 1% and less than 20%, resistance between the 2-3conductive semiconductor layer 127 c and the second electrode decreases,and thus the operating voltage may be lowered. Accordingly, it ispossible to enhance the electrical characteristics. The thickness of the2-3 conductive semiconductor layer 127 c may be greater than 1 nm andless than 10 nm. Accordingly, it is possible to alleviate the lightabsorption problem.

The 2-2 conductive semiconductor layer 127 b may have a smallerthickness than the 2-1 conductive semiconductor layer 127 a. The ratioof the thickness of the 2-1 conductive semiconductor layer 127 a and thethickness of the 2-2 conductive semiconductor layer 127 b may range from1.5:1 to 20:1. When the thickness ratio is less than 1.5:1, the 2-1conductive semiconductor layer 127 a is so thin that the electriccurrent injection efficiency may decrease. Also, when the thicknessratio is greater than 20:1, the 2-2 conductive semiconductor layer 127 bis so thin that there may be a reduction in ohmic reliability.

The 2-1 conductive semiconductor layer 127 a may have an aluminumcomposition decreasing away from the active layer 126. Also, the 2-2conductive semiconductor layer 127 b may have an aluminum compositiondecreasing away from the active layer 126. Accordingly, the aluminumcomposition of the 2-3 conductive semiconductor layer 127 c may be inthe range of 1% to 10%.

However, the present invention is not limited thereto, and the aluminumcompositions of the 2-1 conductive semiconductor layer 127 a and the 2-2conductive semiconductor layer 127 b may, instead of having a continuousdecrease, include some sections in which there is no decrease.

In this case, the 2-2 conductive semiconductor layer 127 b may have agreater reduction in aluminum composition than the 2-1 conductivesemiconductor layer 127 a. That is, the 2-2 conductive semiconductorlayer 127 b may have a greater variation in aluminum composition in athickness direction than the 2-1 conductive semiconductor layer 127 a.Here, the thickness direction may refer to a direction from the firstconductive semiconductor layer 124 to the second conductivesemiconductor layer 127 or a direction from the second conductivesemiconductor layer 127 to the first conductive semiconductor layer 124.

The 2-1 conductive semiconductor layer 127 a should have a greaterthickness than the 2-2 conductive semiconductor layer 127 b and have ahigher aluminum composition than the well layer 126 a. Accordingly, the2-1 conductive semiconductor layer 127 a may have a relatively gradualreduction in aluminum composition.

However, the 2-2 conductive semiconductor layer 127 b has a smallthickness and has a large variation in aluminum composition.Accordingly, the 2-2 conductive semiconductor layer 127 b may have arelatively high reduction in aluminum composition.

FIG. 26 is a conceptual view of a semiconductor device according to afourth embodiment of the present invention.

The above-described configuration of the semiconductor structure 120 maybe applied to a semiconductor structure 120 of FIG. 26 as it is.

A plurality of recesses 128 may extend from a first surface of a secondconductive semiconductor layer 127 to even a portion of a firstconductive semiconductor layer 124 through an active layer 126. A firstinsulation layer 131 may be disposed inside each of the recesses 128 toelectrically insulate a first conductive layer 165 from the secondconductive semiconductor layer 127 and the active layer 126.

A first electrode 142 may be disposed on top of each of the recesses 128and electrically connected with the first conductive semiconductor layer124. A second electrode 246 may be formed under the second conductivesemiconductor layer 127.

As described above, a first surface 127G of the second conductivesemiconductor layer 127 being in contact with the second electrode 246may have an aluminum composition ranging from 1% to 10%, and thus it ispossible to facilitate injection of electric current.

Each of the first electrode 142 and the second electrode 246 may be anohmic electrode. Each of the first electrode 142 and the secondelectrode 246 may be made of at least one of indium tin oxide (ITO),indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminumzinc oxide (IAZO), indium gallium zinc oxide (IGZO), indium gallium tinoxide (IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO),gallium zinc oxide (GZO), IZO nitride (IZON), Al—Ga ZnO (AGZO), In—GaZnO (IGZO), ZnO, IrOx, RuOx, NiO, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO,Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, Mg, Zn, Pt, Au, and Hf, butis not limited thereto.

A second electrode pad 166 may be disposed in an edge region of thesemiconductor device. The second electrode pad 166 may have a recessedcentral portion and thus have a top surface including a concave part anda convex part. A wire (not shown) may be bonded to the concave portionof the top surface. Accordingly, since the bonding area increases, thesecond electrode pad 166 and the wire may be strongly bonded to eachother.

The second electrode pad 166 may serve to reflect light. Thus, as thesecond electrode pad 166 gets closer to the semiconductor structure 120,it is possible to better enhance light extraction efficiency.

The convex portion of the second electrode pad 166 may be higher thanthe active layer 126. Accordingly, the second electrode pad 166 mayenhance light extraction efficiency and control an orientation angle byupwardly reflecting light emitted from the active layer 126 in adirection horizontal to the device.

The first insulation layer 131 is partially open under the secondelectrode pad 166 so that the second conductive layer 150 and the secondelectrode 246 may be electrically connected to each other.

A passivation layer 180 may be formed on top of and on the side of thesemiconductor structure 120. The passivation layer 180 may be in contactwith the first insulation layer 131 in a region adjacent to the secondelectrode 246 or in the lower portion of the second electrode 246.

An opening of the first insulation layer 131 where the second electrodepad 166 is in contact with the second conductive layer 150 may have awidth d22 ranging, for example, from 40 μm to 90 μm. When the width d22is less than 40 μm, the operating voltage may rise. When the width d22is greater than 90 μm, it may be difficult to secure a processing marginfor preventing exposure of the second conductive layer 150. When thesecond conductive layer 150 is exposed outside the second electrode 246,there may be a reduction in reliability of the device. Accordingly, thewidth d22 may preferably range from 60% to 95% of the entire width ofthe second electrode pad 166.

The first insulation layer 131 may electrically insulate the firstelectrode 142 from the active layer 126 and the second conductivesemiconductor layer 127. Also, the first insulation layer 131 mayelectrically insulate the second conductive layer 150 from the firstconductive layer 165.

The first insulation layer 131 may be made of at least one materialselected from a group consisting of SiO2, SixOy, Si3N4, SixNy, SiOxNy,Al₂O₃, TiO2, and AlN, but is not limited thereto. The first insulationlayer 131 may be formed as a single or multiple layers. For example, thefirst insulation layer 131 may be a distributed Bragg reflector (DBR)having a multi-layered structure including an Si oxide or a Ti compound.However, the present invention is not limited thereto, and the firstinsulation layer 131 may include various reflective structures.

When the first insulation layer 131 performs a reflection function, thefirst insulation layer 131 may upwardly reflect light emittedhorizontally from the active layer 126, thereby enhancing lightextraction efficiency. As the number of recesses 128 increases, anultraviolet semiconductor device may have more effective lightextraction efficiency than a semiconductor device that emits blue light.

The second conductive layer 150 may cover the lower portion of thesecond electrode 246. Accordingly, the second electrode pad 166, thesecond conductive layer 150, and the second electrode 246 may form oneelectrical channel.

The second conductive layer 150 may cover the second electrode 246 andmay be in contact with the side surface and the bottom surface of thefirst insulation layer 131. The second conductive layer 150 may be madeof a material having high adhesion strength to the first insulationlayer 131 and may also be made of at least one material selected from agroup consisting of Cr, Al, Ti, Ni, and Au, or an alloy thereof. Thesecond conductive layer 150 may be made as a single or multiple layers.

When the second conductive layer 150 is in contact with the side surfaceand the top surface of the first insulation layer 131, it is possible toenhance thermal and electrical reliability of the second electrode 246.Also, the second conductive layer 150 may have a reflection function forupwardly reflecting light emitted from a gap between the firstinsulation layer 131 and the second electrode 246.

The second insulation layer 132 may electrically insulate the secondconductive layer 150 from the first conductive layer 165. The firstconductive layer 165 may be electrically connected to the firstelectrode 142 through the second insulation layer 132.

The first insulation layer 131 may have a thickness that is larger thanthe second electrode 246 and smaller than the second insulation layer132. For example, the thickness of the first insulation layer 131 mayrange from 300 nm to 700 nm. When the thickness is less than 300 nm,electrical reliability may deteriorate. When the thickness is greaterthan 700 nm and the second conductive layer 150 is disposed on the topsurface and side surface of the first insulation layer 131, the secondconductive layer 150 may have poor step coverage characteristics,thereby causing a detachment or crack. When a detachment or crack iscaused, there may be a deterioration in the electric reliability or areduction of the light extraction efficiency.

The thickness of the second insulation layer 132 may range from 400 nmto 1000 nm. When the thickness is less than 400 nm, electricalreliability may deteriorate when the device operates. When the thicknessis greater than 1000 nm, reliability may be reduced due to a pressure ora thermal stress applied to the device when the device is processed, andalso the cost of the device may increase due to a long processing time.The thicknesses of the first insulation layer 131 and the secondinsulation layer 132 are not limited thereto.

The first conductive layer 165 and a junction layer 160 may be disposeddepending on the shape of the bottom surface of the semiconductorstructure 120 and the shape of the recesses 128. The first conductivelayer 165 may be made of a material with high reflectance. For example,the first conductive layer 165 may contain aluminum. When the firstconductive layer 165 contains aluminum, the first conductive layer 165may serve to upwardly reflect light emitted from the active layer 126,thereby enhancing light extraction efficiency.

The junction layer 160 may contain a conductive material. For example,the junction layer 160 may contain a material selected from a groupconsisting of gold, tin, indium, aluminum, silicon, silver, nickel, andcopper, or an alloy thereof.

A substrate 170 may be made of a conductive material. For example, thesubstrate 170 may contain a metal or a semiconductor material. Thesubstrate 170 may be made of a metal having good electrical conductivityand/or thermal conductivity. In this case, heat generated duringoperation of the semiconductor device may be quickly released to theoutside.

The substrate 170 may contain a material selected from a groupconsisting of silicon, molybdenum, tungsten, copper, and aluminum, or analloy thereof.

A square wave pattern may be formed on top of the semiconductorstructure 120. The square wave pattern may enhance the extractionefficiency for light emitted from the semiconductor structure 120. Thesquare wave pattern may have a different average height depending onultraviolet wavelengths. For UV-C, the average height ranges from 300 nmto 800 nm. When the height ranges from 500 nm to 600 nm, it is possibleto enhance light extraction efficiency.

FIG. 27 is a plan view of FIG. 26 , and FIG. 28 is a sectional viewtaken along A-A of FIG. 27 .

Referring to FIGS. 27 and 28 , each of the recesses 128 may have adiameter ranging from 20 μm to 70 μm. The diameter of each of therecesses 128 may be the maximum diameter formed on the first surface127G of the second conductive semiconductor layer. When the diameter ofthe recess 128 is less than 20 μm, it is difficult to secure aprocessing margin for forming the first electrode 142 disposed therein,and thus the reliability of the semiconductor device may be reduced.When the diameter of the recess 128 is greater than 70 μm, the area ofthe active layer 126 decreases and thus the light emission efficiencymay deteriorate.

An area of where a plurality of first electrodes 142 are in contact withthe first conductive semiconductor layer 124 may range from 7.4% to 20%or from 10% to 20% of the maximum horizontal sectional area of thesemiconductor structure 120.

When the area of the plurality of first electrodes 142 is less than7.4%, electric current spreading characteristics cannot be sufficient,and thus the optical output power decreases. When the area is greaterthan 20%, the areas of the active layer 126 and the second electrode 246excessively decrease, and thus the operating voltage increases and theoptical output power decreases.

Also, the total area of the plurality of recesses 128 may range from 10%to 30% or from 13% to 30% of the maximum horizontal sectional area ofthe semiconductor structure 120. When the total area of the recesses 128does not fall within this range, it may be difficult to keep the totalarea of the first electrode 142 within the range of 7.4% to 20%. Also,there are an increase in operating voltage and a decrease in opticaloutput power.

The area of the first surface 127G of the second conductivesemiconductor layer 127 may be equal to the maximum horizontal area ofthe semiconductor structure 120 minus the total area of the recesses128. For example, the area of the first surface of the second conductivesemiconductor layer 127 may range from 70% to 90% of the maximumhorizontal area of the semiconductor structure 120.

The first surface 127G of the second conductive semiconductor layer 127may include a plurality of first regions 127G-1 surrounding theplurality of recesses 128 and a second region 127G-2 disposed betweenthe plurality of first regions 127G-1, when viewed from the top.

The first region 127G-1 may indicate the sum of spaces S11 between thesecond electrode 246 and outer circumferential surfaces of the recesses128. The area of the first region may range from 1% to 20%.

The second region 127G-2 may be the entire region except the pluralityof first regions 127G-1. The second electrode 246 may be entirelydisposed on the second region 127G-2.

The second region 127G-2 may range from 50% to 89% or from 50% to 70% ofthe maximum horizontal sectional area of the semiconductor structure120. The area of the second region 127G-2 may be an area of where thesecond electrode 246 is in contact with the second conductivesemiconductor layer 127.

When the second area 127G-2 is less than 50%, the area of the secondelectrode 246 is so small that the operating voltage may increase andhole injection efficiency may decrease.

When the second area 127G-2 exceeds 89%, the area of the first electrodeis so relatively small that electron injection efficiency may decrease.Depending on the product, when the second region 127G-2 exceeds 89%,electrical characteristics may be deteriorated. Accordingly, the secondregion may be freely designed to be within the aforementioned range inconsideration of optical and electrical characteristics depending onrequirements of an application field to which a product will be applied.

An area of where the first electrode 142 is in contact with the firstconductive semiconductor layer 124 is inversely proportional to an areaof where the second electrode 246 is in contact with the secondconductive semiconductor layer 127. That is, when the number of recesses128 is increased to increase the number of first electrodes 142, thearea of the second electrode 246 decreases. Accordingly, in order toimprove the electrical and optical characteristics, the spreadingcharacteristics for electrons and holes should be balanced. Accordingly,it may be important to adjust the area of the first electrode and thearea of the second electrode at an appropriate rate.

The ratio of the area of where the plurality of first electrodes 142 arein contact with the first conductive semiconductor layer 124 to the areaof where the second electrode 246 is in contact with the secondconductive semiconductor layer 127 (area of first electrode:area ofsecond electrode) may range from 1:3 to 1:9.

When the area ratio is greater than 1:9, the area of the first electrodeis so relatively small that the electric current spreadingcharacteristics may deteriorate. Also, when the area ratio is less than1:3, the second area is so relatively small that the electric currentspreading characteristics may deteriorate.

The ratio of the entire area of the plurality of first regions 127G-1 tothe area of the second region 127G-2 may range from 1:2.5 to 1:90. Whenthe area ratio is less than 1:2.5, a sufficient ohmic area of the secondelectrode 246 cannot be secured, and thus there may be a reduction inelectrical optical characteristics. When the area ratio is greater than1:90, the area of the first region 127G-1 is so small that it may bedifficult to secure a processing margin.

Referring to FIG. 28 , the first surface 127G of the second conductivesemiconductor layer 127 may include a 1-1 surface S10 disposed betweentwo adjacent recesses 128. The 1-1 surface S10 may include a firstsection S11 where the second electrode 246 is not disposed and a secondsection S12 where an electrode is disposed. The 1-1 surface S10 may havea width ranging from 17 μm to 45 μm.

When the width of the 1-1 surface S10 is less than 17 μm, a separationdistance between the recesses 128 is so small that the disposition areaof the second electrode 246 may be reduced and thus electricalcharacteristics may deteriorate. When the width is greater than 45 μm,the separation distance between the recesses 128 is so large that thedisposition area of the first electrode 142 may be reduced and thuselectrical characteristics may deteriorate.

The first section S11 may be a unit section that forms the first region127G-1. Also, the second section S12 may be a unit section that formsthe second region 127G-2. The second section S12 may have a greaterwidth in a first direction than the first section S11. The width of thefirst section S11 in the first direction (a distance from a recess tothe second electrode) may range from 1 μm to 15 μm.

When the width of the first section S11 is less than 1 μm, it may bedifficult for an extension part 131 a of the first insulation layer tobe disposed on the first surface 127G due to a processing margin.Accordingly, the electrical characteristics may deteriorate. When thewidth of the first section S11 is greater than 15 μm, a distance betweenthe second electrode 246 and the first electrode 142 is so excessivelylarge that the electrical characteristics may deteriorate. Accordingly,the width of the first section S11 in the first direction may be withinthe aforementioned range in consideration of the processing margin andthe electrical characteristics.

The second electrode 246 may have the extension part 131 a of the firstinsulation layer 131 and a separation region S13 having a width of 4 μmor less. When the width of the separation region S13 is greater than 4μm, the disposition area of the second electrode 246 is so small thatthere may be an increase in operating voltage. However, the presentinvention is not limited thereto, and the separation region S13 may notbe formed because of various reasons such as a processing method. Inthis case, it is possible to advantageously enlarge the region where thesecond electrode 246 may be disposed.

The second conductive layer 150 may fully surround the second electrode246 and may be in contact with the side surface and the bottom surfaceof the first insulation layer 131. When the second conductive layer 150is in contact with the side surface and the top surface of the firstinsulation layer 131, it is possible to enhance thermal and electricalreliability of the second electrode 246. Also, it is possible to have afunction of upwardly reflecting incident ultraviolet light.

When the second conductive layer 150 fully cover the second electrode246, the area of the second conductive layer 150 increases, and thus anarea capable of reflecting light increases. Thus, it is possible toenhance the light extraction efficiency of the semiconductor device.That is, ultraviolet light passing through the first section S11 and thesecond section S12 may be reflected by the second conductive layer 150.

The second conductive layer 150 may form a Schottky junction with thesecond conductive semiconductor layer 127 in the separation region S13.Accordingly, it is possible to facilitate spreading of electric current.

The first surface 127G may have an average roughness kept at or below 7nm. When the average roughness is greater than 7 nm, a boundary surfacebetween the second electrode 246 and the second conductive layer 150 isso rough that there may be a decrease in reflectance. The averageroughness may be a value obtained by calculating a difference in heightof a square wave pattern formed on the first surface 127G. The averageroughness may be a root-mean-square (RMS) value measured by using anatomic force microscopy (AFM).

FIG. 29 is a plan view of a second conductive layer, FIG. 30 is a planview showing a second conductive layer having a minimum area, and FIG.31 is a plan view showing a second conductive layer having a minimumarea.

Referring to FIG. 29 , the second conductive layer 150 may cover themaximum area of the semiconductor structure 120 except the region of therecesses 128. According to such a configuration, the second conductivelayer 150 may fully cover the second electrode 246 and the secondconductive semiconductor layer 127, and thus it is possible to increasethe light extraction efficiency.

However, the present invention is not limited thereto, and the secondconductive layer 150 may be disposed only under the second electrode 246as necessary. That is, the second conductive layer 150 may have asmaller area than the second electrode 246.

An area of the second conductive layer 150 overlapping with the maximumhorizontal area (the first area) of the semiconductor structure 120 mayrange from 44% to 180% of the area of the second electrode 246. Theentire area of the second conductive layer 150 may even include a regionother than the semiconductor structure (e.g., a region of the secondelectrode pad).

The area of the second conductive layer 150 overlapping with the maximumarea of the semiconductor structure 120 may range from 40% to 90%. Whenthe area of the second conductive layer 150 overlapping with thesemiconductor structure 120 is less than 40%, efficiency of electriccurrent injected into the second electrode 246 is reduced or an areacapable of reflecting light incident onto the second conductive layer150 through the second electrode 246 is small. Thus, the lightextraction efficiency may be reduced. When the area of the secondconductive layer 150 overlapping with the semiconductor structure 120 is90%, the second conductive layer 150 may cover the entire area of thesemiconductor structure 120 except the region of the recesses 128.

As described above, the area of the second electrode 246 may range from50% to 89% of the maximum horizontal sectional area of the semiconductorstructure 120.

Referring to FIGS. 30 and 31 , when the second conductive layer 150 hasa smaller area than the second electrode 246, the second electrode 246may be exposed through a gap of the second conductive layer 150.

In this case, the second conductive layer 150 may cover only a portionof the second electrode 246. Also, the second conductive layer 150 mayreflect only light having entered the second electrode 246. However,when the device operates at high electric current, it is possible toalleviate a reduction of reliability of the device due to migration ofatoms constituting the second conductive layer 150.

That is, depending on the purpose of an application field of thesemiconductor device, the second conductive layer 150 may be disposed tofully surround the second electrode 246 and may be disposed on only thesecond electrode 246.

FIG. 32 is a diagram illustrating a configuration of the secondconductive layer, FIG. 33 is a first modification of FIG. 32 , and FIG.34 is a second modification of FIG. 32 .

Referring to FIG. 32 , the second electrode 246 may have a thickness d5ranging from 1 nm to 15 nm or from 1 nm to 5 nm. When the thickness d5of the second electrode 246 is less than 15 nm or 5 nm, the amount ofabsorbed light may be reduced. The second electrode 246 may be thinnerthan the first insulation layer.

When the thickness d5 of the second electrode 246 is less than 1 nm, itis difficult to appropriately place the second electrode 246, and thusthe electrical characteristics may be deteriorated. When the thicknessd5 exceeds 15 nm, light absorption is high, and thus the lightextraction efficiency of the semiconductor device may be reduced. Also,when the thickness of the second electrode 246 exceeds 5 nm, the amountof light absorbed by the second electrode 246 increases, and thus theoptical characteristics of the semiconductor device may be deteriorated.However, it is possible to enhance the electrical characteristics.Accordingly, the second electrode may be freely designed to have athickness within the aforementioned range according to characteristicsrequired in an application field to which a product will be applied.

The second conductive layer 150 may include a reflective layer 151containing aluminum and a first intermediate layer 152 disposed betweenthe second electrode 246 and the reflective layer 151. An oxide film maybe formed between the second electrode 246 and the second conductivelayer 150 due to high temperature and high pressure generated during theprocess. In this case, resistance between the second electrode 246 andthe second conductive layer 150 increases, and thus it is possible tofacilitate injection of electric current. Accordingly, the electriccharacteristics of the semiconductor device may be deteriorated. In anembodiment, the first intermediate layer 152 may be disposed between thereflective layer 151 and the second electrode 246 to enhance adhesionstrength therebetween and also prevent occurrence of an oxide film.

The first intermediate layer 152 may contain at least one of chromium(Cr), titanium (Ti), and nickel (Ni). The thickness d6 of the firstintermediate layer 152 may range from 0.7 m to 7 nm. When the thicknessis less than 0.7 m, an adhesion effect and an electric current spreadingprevention effect may be reduced. When the thickness is greater than 7nm, the amount of absorbed ultraviolet light may increase.

The first intermediate layer 152 may further contain aluminum. In thiscase, it is possible to enhance adhesion strength between the firstintermediate layer 152 and the reflective layer 151. Also, the firstintermediate layer 152 is in contact with the first surface 127G in aseparation region, and thus it is possible to improve electric currentspreading characteristics.

The thickness ratio (d5:d7) of the second electrode 246 to thereflective layer 151 may range from 1:2 to 1:120. The thickness d7 ofthe reflective layer 151 may range from 30 nm to 120 nm. When thethickness of the reflective layer 151 is less than 30 nm, reflectance isreduced in an ultraviolet wavelength band. Even when the thickness isgreater than 120 nm, reflective efficiency hardly increases.

Referring to FIG. 33 , a second intermediate layer 153 may be disposedunder the reflective layer 151. The second intermediate layer 153 mayprevent atoms of the reflective layer 151 from migrating to an adjacentlayer and thus may alleviate a reduction in reliability of thesemiconductor device. The second intermediate layer 153 may contain atleast one of Ni, Ti, No, Pt, and W and may have a thickness ranging from50 nm to 200 nm.

Referring to FIG. 34 , a third intermediate layer 154 may be disposedunder the second intermediate layer 153. The third intermediate layer154 is a layer for bonding to another layer and may contain Au, Ni, etc.

FIG. 35 is a conceptual view of a semiconductor device according to afifth embodiment of the present invention, FIG. 36 is a plan view ofFIG. 35 , FIG. 37 is an enlarged view of a part B-1 of FIG. 36 , andFIG. 38 is an enlarged view of a part B-2 of FIG. 36 .

Referring to FIG. 35 , the semiconductor structure 120 described withreference to FIGS. 1 to 3 and the configuration of each of the layersdescribed with reference to FIG. 4 may be applied to the semiconductordevice according to this embodiment as they are. According to anembodiment, a plurality of second electrodes 246 may be disposed on thefirst surface 127G of the second conductive semiconductor layer 127disposed between two recesses 128.

Referring to FIGS. 36 to 38 , the first surface 127G may include firstregions 127G-1 surrounding recesses 128, second regions 127G-2surrounding the first regions 127G-1, and third regions 127G-3 disposedbetween the second regions 127G-2.

Here, a first region 127G-1 may be a region between a second electrode246 and a recess 128. For example, the first region 127G-1 may aring-shaped area. The area of the first region 127G-1 may range from 1%to 20% of the maximum horizontal area of the semiconductor structure120.

The second regions 127G-2 may have the entire area except the recesses128 and the first regions 127G-1. For example, the second regions 127G-2may each have an inner circular shape and an outer polygonal shape. Forexample, the second regions 127G-2 may each have an outer octagonalshape, but is not limited thereto. The second regions 127G-2 may bepartitioned by the third regions 127G-3. The third regions 127G-3 may bedisposed between the plurality of second regions 127G-2. The thirdregions 127G-3 may each be a region with an electric current density of40% or less with respect to the first electrode 142 having an electriccurrent density of 100%. Accordingly, the third regions 127G-3 may eachhave a low probability of participating in light emission. According toan embodiment, the third regions 127G-3, which has a low contribution tolight emission, may be configured as a reflective region to increase thelight extraction efficiency.

The first surface 127G may further include a fourth region 127G-4disposed between a border region of the first surface 127G and the thirdregions 127G-3.

The second electrode 246 may include a 2-1 electrode 246 a disposed inthe second regions 127G-2 and a 2-2 electrode 246 b disposed in thefourth region 127G-4.

The second electrode 246 may contain a metal or metal oxide with lowresistance. However, the second electrode 246 reflects or transmitsvisible light, but absorbs ultraviolet light.

Accordingly, there is a need to reflect light emitted from the activelayer 126 to the second conductive semiconductor layer 127 by decreasingthe area of the second electrode 246 as long as the electricalcharacteristics are not significantly deteriorated. In this case, it ispossible to secure the reflective region by narrowing the second region127G-2 where the second electrode 246 is disposed and widening the thirdregion 127G-3. Since the second conductive layer 150 is entirelydisposed on the first surface 127G, light incident onto the third region127G-3 may be reflected by the second conductive layer 150.

That is, according to an embodiment, the third regions 127G-3, which hasa low contribution to light emission, may be utilized as the reflectiveregion.

A first contact area of where the first surface 127G and the secondelectrode 246 are in contact with each other (the sum of the secondregion and the fourth region of FIG. 36 ) may range from 35% to 60% ofthe maximum area of the semiconductor structure 120. When the firstcontact area is less than 35%, the electric current spreading efficiencymay be reduced. Also, when the first contact area exceeds 60%, the areaof the third region 127G-3 is so small that the light extractionefficiency may decrease.

A second contact area of the first surface 127G and the second electrode246 being not in contact with each other (the sum of the first regionand the third region of FIG. 36 ) may range from 10% to 55% of themaximum area of the semiconductor structure 120. When the second contactarea is less than 10%, it is difficult to have sufficient reflectiveefficiency. When the second contact area is greater than 55%, the areaof the second region 127G-2 is so small that there may be a decrease inelectric current spreading efficiency.

The ratio of the second contact area to the first contact area may rangefrom 1:0.7 to 1:6. When this relationship is satisfied, the electriccurrent spreading efficiency is sufficient, and thus it is possible toenhance the optical output power. Also, a sufficient reflective regionis secured, and thus it is possible to enhance the light extractioneffect.

Referring to FIG. 38 , the separation distance d1 between the thirdregion 127G-3 and a border of the first surface 127G may range from 1.0μm to 10 μm. When the separation distance d1 is less than 1.0 μm, themargin is so small that the second conductive layer 150 may not beappropriately formed, and thus there may be a reduction in reliability.Also, when the separation distance d1 is greater than 10 μm, the area ofthe second electrode 246 is so small that the electrical characteristicsof the semiconductor device may be deteriorated.

FIG. 39 is a sectional view taken along B-B of FIG. 37 .

Referring to FIG. 39 , the first surface 127G of the second conductivesemiconductor layer 151 may include a 1-1 surface S10 disposed betweentwo recesses 128 that are most adjacent to each other in a firstdirection (the X direction). Here, the first direction may be adirection perpendicular to the thickness direction of the semiconductorstructure 120.

The 1-1 surface S10 may include a first section S11 where secondelectrodes 246 are disposed apart from each other in the first directionand a second section S12 placed between the second electrodes 246. Thesecond conductive layer 150 may be disposed in the first section S11 andthe second section S12. The entire width of the 1-1 surface S10 mayrange from 17 μm to 45 μm.

The entire width of the first section S11 in the first direction mayrange from 12 μm to 24 μm. The first section S11 may include twopartition regions at both sides of the second section S12. The partitionregions may have a width ranging from 6 μm to 12 μm.

When the entire width of the first section S11 is less than 12 μm, thearea of the second electrode 246 is so small that there may be adecrease in electric current spreading efficiency. When the entire widthis greater than 24 μm, the second section S12 is so small that thereflective efficiency may be decreased.

The width of the second section S12 in the first direction may rangefrom 5 μm to 16 μm. When the width of the second section S12 in thefirst direction is less than 5 μm, it is difficult to secure asufficient reflective region. When the width is greater than 16 μm, thesecond electrode 246 is narrowed.

The second section S12 may be disposed in a region with an electriccurrent density of 40% or less with respect to the first electrode 142having an electric current density of 100%. A first distance W2+S13+S11between the second section S12 and the center of the recess 128 may beat least 17 μm. The radius of the bottom surface of the recess 128 mayrange from 10 μm to 35 μm, the width of the third section S13 may rangefrom 1 μm to 5 μm, and the width of the first section S11 may range from6 μm to 12 μm. Accordingly, the maximum separation distance may begreater than or equal to 52 μm.

The second section S12 may be disposed in a region with an electriccurrent density of 40% or less from among regions disposed at least 17μm apart from the center of the recess 128. For example, the secondsection S12 may be disposed in a region disposed 40 μm or more apartfrom the center of the recess 128.

When a plurality of recesses 128 are present in the semiconductordevice, second sections S12 disposed 40 μm or more apart from therecesses 128 may overlap with each other. Accordingly, the overlap areaof the second sections S12 may be adjusted according to a distancebetween the recesses 128.

In this case, the second section S12 may include a point correspondingto ½ of the width of the 1-1 surface S10 in the first direction. Thepoint corresponding to ½ of the width of the 1-1 surface S10 in thefirst direction is a region between two adjacent recesses 128 and islikely to have a low electric current density. However, the presentinvention is not limited thereto. When the plurality of recesses hasdifferent diameters, the second section S12 may not necessarily includea point corresponding to ½ of the width in the first direction.

The third section S13 may be a region between the second electrode 246and the recess 128. The width of the third section S13 in the firstdirection may range from 1 μm to 5 μm.

The ratio of the width of the second section S12 to the entire width ofthe first section S11 may range from 1:0.7 to 1:5. When the width ratiorange is satisfied, the ratio of the second contact area to the firstcontact area may be maintained in the range of 1:0.7 to 1:6.Accordingly, it is possible to enhance the electric current spreadingefficiency and the light extraction effect.

FIG. 40 is a first modification of FIG. 39 .

Referring to FIG. 40 , the second conductive layer 150 may include areflective groove 150-1 in the second section S12. Light incident ontothe second section S12 may be reflected along a propagation path changedby the reflective groove 150-1. According to such a configuration, it ispossible to reflect light in various directions, thus enhancinguniformity.

An inclined surface may have an angle θ5 greater than 90 degrees andless than 150 degrees. When the angle of the inclined surface is lessthan 90 degrees or greater than 150 degrees, it may be difficult tovariously change a reflection angle of incident light. The angle of theinclined surface may be defined as an angle formed between the bottomsurface and the inclined surface.

The depth of the reflective groove 150-1 may be the same as thethickness of the first insulation layer 131. The thickness of the firstinsulation layer 131 may be 110% to 130% of that of the thickness of thesecond electrode 246.

A light transmitting layer 133 may be disposed in the reflective groove150-1. The shape of the light transmitting layer 133 may correspond tothe shape of the reflective groove 150-1. Accordingly, the thickness ofthe light transmitting layer 133 may be the same as the thickness of thereflective groove 150-1. For example, the reflective groove 150-1 may beformed by forming the second conductive layer 150 on the lighttransmitting layer 133.

The material of the light transmitting layer 133 may include variousmaterials capable of transmitting ultraviolet wavelength light. Forexample, the light transmitting layer 133 may contain an insulationlayer material. The light transmitting layer 133 may contain at leastone of SiO2, SixOy, Si3N4, SixNy, SiOxNy, Al2O3, TiO2, and AlN, but isnot limited thereto.

FIG. 41A is a second modification of FIG. 39 , and FIG. 41B is a planview of the second modification.

Referring to FIG. 41A, a sub-recess 127 and a sub-reflective layer 135disposed inside the sub-recess 127 may be disposed in the second sectionS12.

The sub-reflective layer 135 may be disposed inside the sub-recess 127.In detail, the sub-reflective layer 135 may be disposed on the firstinsulation layer 131 inside the sub-recess 127.

As the sub-reflective layer 135, a material with high reflectance in anultraviolet wavelength band may be selected. The sub-reflective layer135 may contain a conductive material. For example, the sub-reflectivelayer 135 may contain aluminum. When the sub-reflective layer 135 has athickness ranging from about 30 nm to about 120 nm, the sub-reflectivelayer 135 may reflect 80% or more of ultraviolet wavelength light.Accordingly, it is possible to prevent light emitted from the activelayer 126 from being absorbed in the semiconductor layer.

Light L1 obliquely emitted by the sub-reflective layer 135 may bereflected upwardly. Accordingly, it is possible to reduce lightabsorption in the semiconductor structure 120 and enhance the lightextraction efficiency. Also, it is also possible to adjust anorientation angle of the semiconductor device.

The sub-reflective layer 135 may cover a portion of the second electrode246. According to such a configuration, light flowing into a spacebetween the first insulation layer 131 and the second electrode 246 maybe reflected upwardly. However, the sub-reflective layer 135, which ismade of aluminum, has relatively poor step coverage, and thus it may notbe preferable to fully cover the second electrode 246.

The thickness of the second electrode 246 may be less than or equal to80% of the thickness of the first insulation layer 131. Thus, it ispossible to solve a problem such as a crack or detachment of thesub-reflective layer 135 or the second conductive layer 150 due to areduction in step coverage which may occur when the sub-reflective layer135 and the second conductive layer 150 are disposed.

The sub-reflective layer 135 may have the same width as the sub-recess127. The width of the first recess 128 and the width of the sub-recess127 may indicate the maximum width formed on the first surface 127G ofthe semiconductor structure 120.

The sub-reflective layer 135 may include an extension part 135 aextending toward the second electrode 246 in the sub-recess 127. Theextension part 135 a may electrically connect second electrodes 246separated by the sub-recess 127.

The sub-reflective layer 135 may be disposed in a separation distancebetween the second electrode 246 and the first insulation layer 131, anda region where a Schottky junction is formed between the sub-reflectivelayer 135 and the second conductive semiconductor layer 127 may bewithin the separation distance. By forming the Schottky junction, it ispossible to facilitate spreading of electric current.

An angle θ4 formed between an inclined portion of the sub-reflectivelayer 135 and the first surface of the second conductive semiconductorlayer 127 may range from 90 degrees to 145 degrees. When the inclineangle θ4 is less than 90 degrees, it is difficult to etch the secondconductive semiconductor layer 127. When the incline angle θ4 is greaterthan 145 degrees, the etched area of the active layer is so large thatthere may be a reduction in light emitting efficiency.

The second conductive layer 150 may cover the sub-reflective layer 135and the second electrode 246. Accordingly, the second electrode pad 166,the second conductive layer 150, the sub-reflective layer 135, and thesecond electrode 246 may form one electrical channel. All theabove-described configurations may be applied as the configuration ofthe second conductive layer 150.

Referring to FIG. 41 , the sub-reflective layer 135 may be disposedbetween the plurality of recesses 128 to define a plurality of lightemitting regions. The areas of the light emitting regions may beadjusted depending on the level of injected electric current and thealuminum composition.

FIG. 42 is a third modification of FIG. 39 .

The second conductive layer 150 may include a reflective layer 151containing aluminum and a first intermediate layer 152 disposed betweenthe second electrode 246 and the reflective layer 151. When the secondelectrode 246 is formed of ITO, oxygen may penetrate into the reflectivelayer 151 to form Al2O3. In this case, the reflective efficiency of thereflective layer 151 is reduced. In an embodiment, the firstintermediate layer 152 may be disposed between the reflective layer 151and the second electrode 246, thereby enhancing adhesion strengththerebetween and also preventing penetration of oxygen.

The first intermediate layer 152 may contain at least one of chromium(Cr), titanium (Ti), and nickel (Ni). The first intermediate layer 152may have a thickness ranging from 0.7 m to 7 nm. The first intermediatelayer 152 may further contain aluminum. In this case, it is possible toenhance adhesion strength between the first intermediate layer 152 andthe aluminum.

The first intermediate layer 152 may be in contact with the firstsurface 127G of the second conductive semiconductor layer 127 in thesecond section S12 and the third section S13. Accordingly, it ispossible to enhance the electric current spreading efficiency by meansof a Schottky junction.

The thickness ratio of the second electrode 246 to the reflective layer151 may range from 1:2 to 1:120. The thickness of the reflective layer151 may range from 30 nm to 120 nm. When the thickness of the reflectivelayer 151 is less than 30 nm, there is a reduction in reflectance in anultraviolet wavelength band. Even when the thickness is greater than 120nm, reflective efficiency hardly increases.

FIG. 43 is a conceptual view of a semiconductor device according to asixth embodiment of the present invention, and FIG. 44 is a plan view ofFIG. 43 .

Referring to FIG. 43 , the above-described configuration of each layermay be applied to the semiconductor device according to this embodimentas it is.

Referring to FIG. 44 , the first surface 127G may include first regions127G-1 having recesses disposed therein and a second region 127G-2disposed between the first regions 127G-1.

The diameter of the first regions 127G-1 may be 1.0 to 1.5 times that ofthe recesses 128. When the diameter of the first regions 127G-1 exceeds1.5 times, the area of the second electrode 246 is so small that theremay be a reduction in electric current spreading efficiency. The firstregions 127G-1 may be a region between the second electrode 246 and therecesses 128.

The second region 127G-2 may be the remaining region other than thefirst regions 127G-1. The second electrode 246 may be disposed on thesecond region 127G-2 as a whole.

The second electrode 246 may contain a metal or metal oxide with lowresistance. Accordingly, the second electrode 246 absorbs ultravioletlight. Accordingly, there is a need to reduce the amount of lightabsorbed by the second electrode 246 by decreasing the area of thesecond electrode 246.

The second conductive layer 150 is disposed on the first regions 127G-1and the second region 127G-2, and thus light incident onto the firstregions 127G-1 may be reflected by the second conductive layer 150.Accordingly, it is possible to increase light extraction efficiency bydecreasing the area of the second region 127G-2 where the secondelectrode 246 is disposed and increasing the area of the first regions127G-1. In this case, it is important to maximally secure a reflectiveregion while securing the area of the second electrode 246 needed tospread electric current.

The area of the second region 127G-2 may range from 35% to 60% of themaximum area of the semiconductor structure 120. When the area of thesecond region 127G-2 is less than 35%, the contact area of the secondelectrode 246 is so small that the electric current spreading efficiencymay be reduced. Also, when the area of the second region 127G-2 exceeds60%, the area of the first regions 127G-1 is so small that the lightextraction efficiency may decrease.

The area of the first regions 127G-1 may range from 10% to 55% of themaximum area of the semiconductor structure 120. When the area of thefirst regions 127G-1 is less than 10%, it is difficult to havesufficient reflective efficiency. When the area of the first regions127G-1 is greater than 55%, the area of the second region 127G-2 is sosmall that there may be a decrease in electric current injectionefficiency.

Accordingly, the ratio of the area of the first regions 127G-1 to thearea of the second region 127G-2 may range from 1:0.7 to 1:6. When thisrelationship is satisfied, the electric current spreading efficiency issufficient, and thus it is possible to enhance the optical output power.Also, a sufficient reflective region is secured, and thus it is possibleto enhance the light extraction effect.

FIG. 45 is a sectional view taken along C-C of FIG. 44 .

The first surface 127G of the second conductive semiconductor layer mayinclude a 1-1 surface S10 disposed between the center of two first andsecond recesses 128 a and 128 b that are most adjacent to each other ina first direction (the X direction). In this case, the first directionmay be a direction perpendicular to the thickness direction of thesemiconductor structure 120.

The 1-1 surface S10 may include a first section S21 and second sectionsS22 a and S22 b disposed between the first section S21 and first andsecond recesses 128 a and 128 b.

The second sections S22 a and S22 b may include a 2-1 section S22 adisposed between the first section S21 and the first recess 128 a and a2-2 section S22 b disposed between the first section S21 and the secondrecess 128 b.

The second electrode 246 may be disposed in the first section S21. Whenthe second electrode 246 is disposed in only the second sections S22 aand S22 b, the electric current density of the second sections S22 a andS22 b may increase, but the electric current density of the firstsection S21 may relatively decrease. Also, when the second electrode 246is disposed in all of the first section S21 and the second sections S22a and S22 b, light absorption may occur in all of the first section S21and the second sections S22 a and S22 b. This may not be beneficial tolight extraction efficiency.

The second conductive layer may be disposed in the first section S21 andthe second sections S22 a and S22 b. Accordingly, the second sectionsS22 a and S22 b where the second electrode 246 is not disposed mayperform a reflection function.

According to an embodiment, it is important to appropriately determine adistance between the first electrode 142 and the second electrode 246 inorder to secure light extraction efficiency while securing an electriccurrent density needed for light emission.

For example, when the area of the first electrode 142 is large, anelectric current spreading region is widened, and thus it is possible toincrease the area of the second sections S22 a and S22 b. Accordingly,it is possible to widen the reflective region. However, when the area ofthe first electrode 142 is small, the electric current spreading regionis narrowed, and thus the second sections S22 a and S22 b may benarrowed.

The ratio of the width of the 2-1 section S22 b in the first directionto the diameter W1 of the first recess 128 a may range from 1:1.25 to1:14. When the ratio is smaller than 1:1.25, the diameter of therecesses 128 is reduced, and thus the area of the first electrode 142decreases. Accordingly, the strength of electric current injectedthrough the first electrode 142 is weakened, and thus the electriccurrent density of the second sections S22 a and S22 b may be reduced.

When the ratio is greater than 1:14, the diameter of the recesses 128 isexcessively increased, and thus the area of the first surface 127G ofthe second conductive semiconductor layer decreases. That is, the widthof the 1-1 surface S10 decreases. As a result, the area of the activelayer 126 decreases, and thus the light emitting region is reduced.

The diameter W1 of the recesses 128 may range from 20 μm to 70 μm. Whenthe diameter of the recesses 128 is less than 20 μm, it is difficult tosecure a processing margin for forming the first electrode 142 disposedtherein. When the diameter of the recesses 128 is greater than 70 μm,the area of the active layer 126 is so small that the light emissionefficiency may deteriorate. Here, the diameter of the recess 128 may bethe maximum diameter formed on the first surface 127G of the secondconductive semiconductor layer.

The width of the first section S21 in the first direction may range from6 μm to 12 μm. When the width is less than 6 μm, the area of the secondelectrode 246 is so small that there may be a decrease in electriccurrent spreading efficiency. When the width is greater than 12 μm, thesecond sections S22 a and S22 b are so small that there may be adecrease in reflective efficiency.

The widths of the 2-1 section S22 a and the 2-2 section S22 b in thefirst direction may range from 5 μm to 16 μm. That is, the entire widthof the second sections S22 a and S22 b may range from 10 μm to 32 μm.When the widths of the 2-1 section S22 a and the 2-2 section S22 b inthe first direction are less than 5 μm, it is difficult to secure asufficient reflective region. When the widths are greater than 16 μm,the second electrode 246 is narrowed.

The ratio of the width of the first section S21 to the entire width ofthe second sections S22 a and S22 b may range from 1:0.8 to 1:5. Whenthe width ratio range is satisfied, the ratio of the area of the firstregions 127G-1 to the area of the second region 127G-2 may be adjustedto be in the range of 1:0.8 to 1:6. Accordingly, it is possible toenhance the electric current spreading efficiency and the lightextraction effect.

The first section S21 may include a point corresponding to ½ of the 1-1surface S10. Since the second electrode 246 is disposed at the center ofthe 1-1 surface S10, the electric current density of the first sectionS21 may increase. Also, since the electric current density of the firstsection S21 increases, electric current is spread in the second sectionsS22 a and S22 b disposed therebetween, and it is possible to secure anelectric current density needed for light emission. However, the presentinvention is not limited thereto. When the diameter of the first recess128 a is different from the diameter of the second recess 128 b, thefirst section S21 may deviate from the point corresponding to ½ of the1-1 surface S10.

FIG. 46 is a first modification of FIG. 45 , and FIG. 47 is a secondmodification of FIG. 45 .

The second conductive layer 150 may include a reflective groove 150-2 inthe second sections S22 a and S22 b. Light incident onto the secondsections S22 a and S22 b may be reflected along a propagation pathchanged by an inclined surface of the reflective groove 150-2. Accordingto such a configuration, it is possible to enhance light uniformity.

The depth of the reflective groove 150-2 may be the same as thethickness of the first insulation layer 131. The thickness of the firstinsulation layer 131 may be equal to 110% to 130% of the thickness ofthe second electrode 246. As described above, the thickness of thesecond electrode 246 may range from 1 nm to 15 nm.

A light transmitting layer 131 b may be disposed in the reflectivegroove 150-2. The shape of the light transmitting layer 131 b maycorrespond to the shape of the reflective groove 150-2. Accordingly, thethickness of the light transmitting layer 131 b may be the same as thethickness of the reflective groove 150-2. For example, the reflectivegroove 150-2 may be formed by disposing the second conductive layer 150on the light transmitting layer 131 b.

The material of the light transmitting layer 131 b may include variousmaterials capable of transmitting ultraviolet wavelength light. Forexample, the light transmitting layer 131 b may include an insulationlayer material. The light transmitting layer 131 b may include at leastone of SiO2, SixOy, Si3N4, SixNy, SiOxNy, Al2O3, TiO2, and AlN, but isnot limited thereto.

The light transmitting layer 131 b may be formed by the first insulationlayer 131 disposed inside the first recess 128 a extending to the secondconductive semiconductor layer. However, the present invention is notlimited thereto, and a separate dielectric layer may be disposed.

Referring to FIG. 47 , the second electrode 246 may have a densitydecreasing away from the center point of the 1-1 surface S10. That is,partitioned second electrodes 246, 246 d, and 246 e may be disposed tohave a size decreasing away from the center. The partitioned secondelectrodes 246 c, 246 d, and 246 e may be produced through selectiveetching by means of a mask.

According to such a configuration, it is possible to increase theelectric current density of the second sections S22 a and S22 b whilemaintaining the electric current density of the first section S21. Also,it is possible to obtain both electric current spreading efficiency andreflective efficiency by maintaining the area ratio of the first sectionS21 to the second sections S22 a and S22 b in the range of 1:0.8 to 1:6.

FIG. 48 is a conceptual view of a semiconductor device package accordingto an embodiment of the present invention, FIG. 49 is a plan view of thesemiconductor device package according to an embodiment of the presentinvention, and FIG. 50 is a modification of FIG. 49 .

Referring to FIG. 48 , the semiconductor device package may include abody 2 with a groove (an opening) 3, a semiconductor device 1 disposedin the body 2, and a pair of lead frames 5 a and 5 b disposed in thebody 2 and electrically connected to the semiconductor device 1. Thesemiconductor device 1 may include all of the above-described elements.

The body 2 may contain a material or a coating layer that reflectsultraviolet light. The body 2 may be formed by stacking a plurality oflayers 2 a, 2 b, 2 c, 2 d, and 2 e. The plurality of layers 2 a, 2 b, 2c, 2 d, and 2 e may be made of the same material or contain differentmaterials. For example, the plurality of layers 2 a, 2 b, 2 c, 2 d, and2 e may contain an aluminum material.

The groove 3 may have a width increasing away from the semiconductordevice and may have an inclined surface having a stepped portion formedtherein.

A light transmitting layer 4 may cover the groove 3. The lighttransmitting layer 4 may be made of glass, but is not limited thereto.The material of the light transmitting layer 4 is not particularlylimited as long as the material can effectively transmit ultravioletlight. The groove 3 may have an empty space formed therein.

Referring to FIG. 49 , a semiconductor device 10 may be disposed on afirst lead frame 5 a and connected with a second lead frame 5 b by meansof a wire. In this case, the second lead frame 5 b may be disposed tosurround the side surface of the first lead frame.

Referring to FIG. 50 , the semiconductor device package may have aplurality of semiconductor devices 10 a, 10 b, 10 c, and 10 d disposedtherein. In this case, the lead frame may include a first lead frame 5a, a second lead frame 5 b, a third lead frame 5 c, a fourth lead frame5 d, and a fifth lead frame 5 e.

The first semiconductor device 10 a may be disposed on the first leadframe 5 a and connected with the second lead frame 5 b by means of awire. The second semiconductor device 10 b may be disposed on the secondlead frame 5 b and connected with the third lead frame 5 c by means of awire. The third semiconductor device 10 c may be disposed on the thirdlead frame 5 c and connected with the fourth lead frame 5 d by means ofa wire. The fourth semiconductor device 10 d may be disposed on thefourth lead frame 5 d and connected with the fifth lead frame 5 e bymeans of a wire.

The semiconductor device may be applied to various kinds of light sourcedevices. For example, conceptually, the light source devices may includea sterilizing device, a curing device, a lighting device, a displaydevice, and a vehicle lamp. That is, the semiconductor device may beapplied to various electronic devices configured to provide light bybeing disposed in housing thereof.

The sterilizing device may have a semiconductor device of an embodimentto sterilize a desired region. The sterilizing device may be applied tohome appliances such as a water purifiers, air conditioners, andrefrigerators, but is not limited thereto. That is, the sterilizingdevice may be applied in various products needing to be sterilized(e.g., medical apparatuses).

For example, a water purifier may have the sterilizing device of anembodiment to sterilize circulating water. The sterilizing device may beplaced at a nozzle or a discharging port through which water circulatesand configured to emit ultraviolet light. In this case, the sterilizingdevice may include a waterproof structure.

The curing device may have a semiconductor device of an embodiment tocure various kinds of liquids. Conceptually, the liquids may includevarious materials that are cured when ultraviolet light is emitted. Forexample, the curing device may cure various types of resins.Alternatively, the curing device may also be applied to cure beautyproducts such as manicure products.

The lighting device may include a light source module including asubstrate and a semiconductor device of an embodiment, a heatdissipation unit configured to dissipate heat of the light sourcemodule, and a power supply unit configured to process or convert anelectric signal from the outside and provide the electric signal to thelight source module. Also, the lighting device may include a lamp, aheadlamp, or a streetlight.

The display device may include a bottom cover, a reflective plate, alight emitting module, a light guide plate, an optical sheet, a displaypanel, an image signal output circuit, and a color filter. The bottomcover, the reflective plate, the light emitting module, the light guideplate, and the optical sheet may constitute a backlight unit.

The reflective plate may be placed on the bottom cover, and the lightemitting module may emit light. The light guide plate may be placed infront of the reflective plate to guide light emitted by the lightemitting module forward. The optical sheet may include a prism sheet orthe like and may be placed in front of the light guide plate. Thedisplay panel may be placed in front of the optical sheet. The imagesignal output circuit may supply an image signal to the display panel.The color filter may be placed in front of the display panel.

When the semiconductor device is used as a backlight unit of a displaydevice, the semiconductor device may be used as an edge-type backlightunit or a direct-type backlight unit.

The semiconductor device may be a laser diode rather than theabove-described light emitting diode.

Like the light emitting device, the laser diode may include a firstconductive semiconductor layer, an active layer, and a second conductivesemiconductor layer that have the above-described structures. The laserdiode may also utilize an electroluminescence phenomenon in which lightis emitted when electric current flows after a p-type first conductivesemiconductor and an n-type second conductive semiconductor are broughtin contact with each other, but has a difference in the directionalityand phase of the emitted light. That is, the laser diode uses stimulatedemission and constructive interference so that light having a specificsingle wavelength may be emitted at the same phase and in the samedirection. Due to these characteristics, the laser diode may be used foran optical communication device, a medical device, a semiconductorprocessing device, or the like.

A light receiving device may include, for example, a photodetector,which is a kind of transducer configured to detect light and convertintensity of the light into an electric signal. The photodetector mayinclude a photocell (silicon and selenium), an optical output element(cadmium sulfide and cadmium selenide), a photodiode (e.g., a PD with apeak wavelength in a visible blind spectral region or a true blindspectral region), a photo transistor, a photomultiplier, a photoelectrictube (vacuum and gas filling), an infra-red (IR) detector, or the like,but is not limited thereto.

Generally, a semiconductor device such as the photodetector may beproduced using a direct bandgap semiconductor having good photoelectrictransformation efficiency. Alternatively, the photodetector may havevarious structures. As the most common structure, the photodetector mayinclude a pin-type photodetector using a p-n junction, a Schottkyphotodetector using a Schottky junction, a metal-semiconductor-metal(MSM) photodetector, or the like.

Like the light emitting device, the photodiode may include a firstconductive semiconductor layer and a second conductive semiconductorlayer that have the above-described structures and may be formed as ap-n junction or a pin structure. The photodiode operates when a reversebias or a zero bias is applied. When light is incident on thephotodiode, electrons and holes are generated such that electric currentflows. In this case, the magnitude of electric current may beapproximately proportional to the intensity of the light incident on thephotodiode.

A photocell or a solar cell, which is a kind of photodiode, may convertlight into electric current. Like the light emitting device, the solarcell may include a first conductive semiconductor layer, an activelayer, and a second conductive semiconductor layer that have theabove-described structures.

Also, the solar cell may be used as a rectifier of an electronic circuitthrough the rectification characteristics of a general diode using a p-njunction and may be applied to an oscillation circuit or the like of amicrowave circuit.

Also, the above-described semiconductor device is not necessarilyimplemented only with semiconductors. Depending on the case, thesemiconductor device may additionally include a metal material. Forexample, a semiconductor device such as the light receiving device maybe implemented using at least one of Ag, Al, Au, In, Ga, N, Zn, Se, P,and As and may be implemented using an intrinsic semiconductor materialor a semiconductor material doped with a p-type dopant or an n-typedopant.

While the present invention has been described with reference toexemplary embodiments, these are just examples and do not limit thepresent invention. It will be understood by those skilled in the artthat various modifications and applications may be made therein withoutdeparting from the essential characteristics of the embodiments. Forexample, elements described in the embodiments above in detail may bemodified and implemented. Furthermore, differences associated with suchmodifications and applications should be construed as being included inthe scope of the present invention defined by the appended claims.

The invention claimed is:
 1. A semiconductor device comprising: asemiconductor structure including a first semiconductor layer, a secondsemiconductor layer, and an active layer; a first electrode provided ona first surface of the first semiconductor layer; a second electrodeprovided on a first surface of the second semiconductor layer; theactive layer being provided between the first surface of the firstsemiconductor layer and a second surface of the second semiconductorlayer that is opposite to the first surface of the second semiconductorlayer; a first insulation layer provided on the first surface of thefirst semiconductor layer, the first surface of the second semiconductorlayer, and a side surface of the active layer, the first insulationlayer and the first electrode being separated on the first surface ofthe first semiconductor layer; and a first cover electrode provided onthe first electrode and the first semiconductor layer, wherein: thefirst electrode includes a first surface facing the first surface of thefirst semiconductor layer and a second surface that is opposite to thefirst surface of the first semiconductor layer, the first electrodeincludes protrusions extending from the second surface of the firstelectrode in a first direction, and a groove provided on the secondsurface of the first electrode and between the protrusions, and thefirst cover electrode extends into the groove of the first electrode. 2.The semiconductor device of claim 1, further comprising an oxide filmbetween the protrusions of the first electrode and the first coverelectrode.
 3. The semiconductor device of claim 1, wherein an upperwidth of at least one of the protrusions ranges from 1 um to 10 um. 4.The semiconductor device of claim 1, wherein the semiconductor structureincludes a non-light emitting region exposing the first conductivesemiconductor layer and a light emitting region protruding over thenon-light emitting region, wherein the light emitting region includesthe active layer and the second conductive semiconductor layer, andwherein the second cover electrode includes a plurality of pad partsdisposed on the light emitting region and a connection part configuredto connect the plurality of pad parts.
 5. The semiconductor device ofclaim 4, wherein the semiconductor structure includes a plurality ofpartition regions defined by a first virtual line passing throughcenters of a first side surface and a third side surface of thesemiconductor structure, which are opposite to each other, and a secondvirtual line passing through centers of a second side surface and afourth side surface of the semiconductor structure, which are oppositeto each other when viewed from a top of the semiconductor structure,wherein the plurality of partition regions includes a first partitionregion including the first side surface and the fourth side surface, asecond partition region including the first side surface and the secondside surface, a third partition region including the second side surfaceand the third side surface, and a fourth partition region including thethird side surface and the fourth side surface.
 6. The semiconductordevice of claim 5, wherein the plurality of pad parts includes a firstpad part disposed in the first partition region, a second pad partdisposed in the second partition region, and a third pad part disposedin the fourth partition region, and wherein the connection part includesa first connection part configured to connect the first pad part withthe second pad part and a second connection part configured to connectthe first pad part with the third pad part.
 7. The semiconductor deviceof claim 6, wherein the first connection part has a width decreasingtoward the first virtual line, and wherein the second connection parthas a width decreasing toward the second virtual line.
 8. Thesemiconductor device of claim 1, wherein the first groove includes agroove or a plurality of grooves disposed apart from each other.
 9. Thesemiconductor device of claim 1, wherein the first cover electrodeoverlaps a section of the first insulation layer on the first surface ofthe first semiconductor layer and in a second direction parallel to thefirst surface of the first semiconductor layer.
 10. The semiconductordevice of claim 9, wherein a first area of the section of the firstinsulation layer overlapped by the first cover electrode in the seconddirection is smaller than a second area of a region of the first surfaceof first semiconductor layer between the first insulation layer and thefirst electrode.
 11. The semiconductor device of claim 10, wherein aratio of the second area to the first area ranges between 1:0.15 and1:1.
 12. The semiconductor device of claim 1, wherein a secondinsulation layer is disposed on the first cover electrode, the secondelectrode, and the first insulation layer.
 13. The semiconductor deviceof claim 12, wherein the second insulation layer includes a firstopening over the first cover electrode and a second opening over thesecond cover electrode, and wherein the semiconductor device furthercomprises: a first bump electrode provided in the first opening of thesecond insulation layer and on the first cover electrode; and a secondbump electrode provided in the second opening of the second insulationlayer and on the second cover electrode.
 14. The semiconductor device ofclaim 1, further comprising a stepped portion extending from the firstsurface of the first conductive semiconductor layer to the first surfaceof the second conductive semiconductor layer.
 15. The semiconductordevice of claim 14, wherein the stepped portion includes a first partwhere the first electrode is disposed, a second part when the secondelectrode is disposed, a third part where the first insulation layer isdisposed between the first part and the second part, and a fourth partwhere the first cover electrode is disposed between the first part andthe third part.
 16. The semiconductor device of claim 1, wherein thesecond cover electrode includes a plurality of second branch electrodesextending in a first plan direction and a second connection electrodeconnecting the plurality of second branch electrodes, and the firstcover electrode includes a plurality of first branch electrodes providedbetween the second branch electrodes and a first connection electrodeconnecting the plurality of first branch electrodes.
 17. Thesemiconductor device of claim 1, wherein each of the first semiconductorlayer and the second semiconductor layer includes a material having anempirical formula In_(x1)Al_(y1)Ga_(1-x1-y1)N (0≤x1≤1, 0<y1≤1,0≤x1+y1≤1), and the semiconductor device emits ultraviolet (UV)-Cradiation.